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  (199)_[2026] "In Situ Evaporated Phosphine Oxide Bifunctional Additive for Efficient Vacuum-Deposited Near-Infrared Perovskite Light-Emitting Diodes" L. Qin, X. Zhang, W. Zhou, J.-W. Kang, S. He*, J. Luo*, Advanced Optical Materials, In Press (2025. 11. 20)

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  2025.11.26

  AbstractVacuum-deposited perovskite light-emitting diodes (PeLEDs) have demonstrated great potential for next-generation light sources. However, vacuum-deposited perovskites suffer from high defect densities due to the lack of sufficient passivation strategies. Herein, an effective in situ passivation strategy for vacuum-deposited PeLEDs using bifunctional tris(4-fluorophenyl)phosphine oxide (TFPPO) additive is introduced. The P═O moieties of TFPPO with lone pair electrons bond with the undercoordinated Pb2+ sites, suppressing the defect formation. Besides, the fluorine functional groups of TFPPO that form hydrogen bonds with the formamidinium cations control their diffusion during the vacuum deposition, thus reducing the crystal grain size. As a result, the uniform and compact TFPPO-incorporated FACsPbI3 thin film enables near-infrared PeLED with a record external quantum efficiency of 14.33%. This work presents a process-compatible defect passivation strategy to advance vacuum-deposited perovskite optoelectronics.Submission: June 29, 2025https://doi.org/10.1002/adom.202502072
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  (198)_[2026] "Light management in perovskite quantum dot light-emitting diodes for active-matrix display" S. He, H. Xie, X. Zhang, W. Zhou, L. Qin, J.-W. Kang*, J. Luo*, ACS Energy Letters, In Submission (2025. 11. 22)

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  2025.11.13

  Abstract: Despite significant progress in optimizing perovskite emitters, enabling the fabrication of high-quality perovskite films with near-unity photoluminescence quantum yield, the advancement of perovskite quantum light-emitting diodes (PeQLEDs) remains hindered by inadequate light-outcoupling efficiency. To address this, we developed high-efficiency PeQLEDs based on formamidinium lead bromide quantum dots (QDs) modified with tris(4-fluorophenyl)phosphine oxide (TFPPO), a material with a low refractive index (n). The TFPPO-modified QDs replace the conventional oleic acid ligands, resulting in a reduced n value (n = 1.63 at 532 nm) compared to pristine QDs (n = 1.67 at 532 nm). This refractive index tailoring effectively minimizes optical energy loss. Additionally, the addition of TFPPO suppressed the defect densities and non-radiative recombination of perovskite films. Further optical optimization is achieved through the use of a low-refractive-index charge transport layer, i.e. PO-T2T as an electron transport layer (ETL) with an average n 1.8, and PFI-modified PEDOT:PSS as a hole transport layer (HTL) with an average n 1.5. Finite-difference time-domain simulations show that these modifications collectively reduced optical confinement within the device structure. As a result, the optimal device achieves a maximum EQE of 21.54%, a 2.2-fold enhancement over the pristine device (9.84%). Additionally, the feasibility of integrating solution-processed PeQLEDs with active-matrix drivers for display applications is demonstrated, underscoring their potential for next-generation display technologies.In Submission (2025. 11. 22)
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  (197)_[2026] "Solvent Engineering and Vacuum Annealing Synergy for Efficient Ambient Inkjet-Printed PHOLEDs" S. Chowdhury, K.-J. Ko, V.V. Satale, W. Zhou, J.-W. Kang* Macromolecular Research, In Press(2025. 09. 29)

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  2025.10.13

  AbstractHigh-boiling solvents are essential for inkjet-printed phosphorescent organic light emitting diodes (PHOLED), but their low vapor pressure leaves residual molecules that form dipolar sites, inducing polaron formation and quenching triplet emission. To overcome this, we introduced a vacuum-assisted annealing (VAA) strategy that removes 80% of ethyl p-toluate and 75% of 3-ethylbiphenyl from Ir(mppy)3-doped green PHOLED films. Efficient solvent removal was confirmed by mass spectroscopy, and photoluminescence decay indicated an extended triplet lifetime. Moreover, nanoscale surface analysis and absorption spectroscopy verified that VAA preserves film uniformity, smoothness, and the electronic structure of the Ir(III) complex. As a result, VAA-treated PHOLEDs achieved an external quantum efficiency (EQE) of 6.4%, a 75% improvement over spin-coated references. Under fully ambient inkjet-printing, devices also reached 4.4% EQE, representing a 30% gain compared to untreated films. This study demonstrates that residual solvent removal is the key bottleneck in printed PHOLEDs and establishes VAA as a simple, polymer-compatible strategy to enhance device performance under ambient, large-area processing conditions.https://doi.org/10.1007/s13233-025-00460-0
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  (196)_[2026] "Low-Temperature ALD-Grown SnOx Interlayer for Scalable and Stable p-i-n Perovskite Solar Cells and Modules" A. Mohamed, H.B. Lee, V.V. Satale, K.-J. Ko, B. Tyagi, D.-H. Kim, J.-W. Kang* Sustainable Energy & Fuels, 10, 245–257 (2026)

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  2025.10.13

  AbstractInverted p i n perovskite solar cells (IPSCs) offer promise for next-generation photovoltaics. However, IPSCs utilizing solution-processed PC61BM as the electron transport layer (ETL) remain less interface-optimized than conventional n i p configurations, restricting their efficiency, stability, and scalability. In this work, we introduce an ultrathin atomic-layer-deposited SnOx (ALD-SnOx) film, fabricated at a low temperature (80 C), as a versatile interfacial modifier to address these shortcomings. This scalable, vapor-phase approach directly addresses the core instability in p i n architectures, effectively remedies morphological defects such as pinholes and phase segregation in PC61BM, significantly enhancing interfacial contact and suppressing charge recombination. Consequently, the champion IPSC incorporating a 10 nm ALD-SnOx interlayer yields a power conversion efficiency (PCE) of 19.2%, representing a remarkable 58% improvement over control devices (PCE 11.3%). The ALD-SnOx interlayer effectively enhances moisture resistance, giving the IPSCs excellent environmental stability. Additionally, the redesigned IPSCs show scalability by effectively generating a large-area ( 12.1 cm2) mini-module with a high PCE ( 14.1%). These findings demonstrate the immense potential of this interfacial engineering approach for the commercial production of scalable, stable, and effective IPSCs.DOIhttps://doi.org/10.1039/D5SE01332A
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  (195)_[2026] "Tunable and Patternable QD Emissive Layers via Spray-Driven Surface Halide Exchange" W. Zhou, S. He, K. Ko, S. Chowdhury, J.-W. Kang* ChemNanoMat, In Press (2025. 12. 24)

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  2025.10.13

  Abstract: All-inorganic CsPbX3 quantum dots combine high efficiency, narrow emission, and solution processability; however, their scalable full-color implementation requires pixel-level patterning with minimal performance loss. Herein, we developed a spray-driven halide exchange strategy that enabled spatially programmable color tuning and patterning of green CsPbBr3 films. By spraying a chlorine-based ligand through a mask, we obtained a surface-confined Br Cl exchange, creating precise patterns without reprocessing the underlying film. After ligand exchange with phenethylammonium chloride (PEACl) at various concentrations, the photoluminescence (PL) peak shifted from 516 nm to 495/462/433 nm, while maintaining a full width at half maximum of approximately 20 nm. In addition, the crystalline phases and surface morphologies of the films were preserved. Furthermore, devices fabricated from halide exchange-treated films successfully converted the emission from green to blue. This strategy achieved an engineering tradeoff between pronounced color tuning and limited efficiency loss, providing a practical route for full-color pixelation on a single substrate.In revision 2025.12.05In accept 2025.12.24
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  (194)_[2026] "Ambient Inkjet-Printed PHOLEDs with Record Efficiency via Dual-SAM Engineering and Eco-Friendly Solvent Design" S. Chowdhury, K. Ko, V.V. Satale, H. Kim, S.-H. Jin*, J.-W. Kang*, Materials Today, In Press (2025. 12 22)

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  2025.06.16

  Highlights Ambient inkjet printing enables scalable fabrication of green PHOLEDs. Dual-SAM modification on ITO boosts hole injection efficiency without HTL. Eco-friendly binary solvent system improves film uniformity by suppressing coffee-ring effect. Novel heteroleptic Ir(III) emitter enhances ink compatibility and charge transport. Record external quantum efficiency of 16.8% achieved in PHOLEDs with inkjet printed EML.AbstractInkjet printing offers a scalable and material-efficient route for fabricating organic light-emitting devices, yet solution-processed phosphorescent OLEDs (PHOLEDs) remain limited by interfacial instability, solvent incompatibility, and poor ambient processability. In this study, we report a high-performance, hole-transport layer (HTL)-free PHOLED fully fabricated under ambient conditions using an inkjet printing strategy based on eco-friendly solvents. A dual self-assembled monolayer (SAM) modification on the ITO anode, combining 2,3,4,5,6-pentafluorobenzoyl phosphonic acid and tricosafluorododecanoic acid, enables efficient charge injection without the need for conventional HTLs. Complementing this, a binary solvent system comprising environmentally benign components is engineered to suppress the coffee-ring effect and significantly improve film uniformity. Furthermore, a newly designed heteroleptic Ir(III) emitter with tailored solubilizing groups enhances ink compatibility and charge-transport properties. The resulting devices achieve a record-high external quantum efficiency of 16.8% under ambient processing conditions, marking a new benchmark for inkjet-printed PHOLEDs. This work demonstrates a synergistic approach to interfacial engineering and eco-conscious solvent design, offering a scalable, sustainable pathway toward high-efficiency, vacuum-free OLED technologies.In Submission (2025. 08. 19)In Revision (2025. 10. 15)https://doi.org/10.1016/j.mattod.2025.12.017
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  (193)_[2026] "Tuning Transition Dipole Moment Alignment via Bifunctional Ligands in Perovskite Nanocrystal Light-Emitting Diodes" W. Weiyang, S. Ham, H.B. Lee, J. Luo, S. He*, J.-H. Lee*, J.-W. Kang*, Advanced Materials, In Press (2025)

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  2025.06.16

  ABSTRACTPerovskite quantum dot light-emitting diodes (PeQLEDs) are promising for display and lighting applications. As internal quantum efficiencies approach 1, enhancing photon extraction becomes critical due to severe optical losses. Herein, we proposed a facile ligand exchange strategy with bifunctional 1,5-naphthalenedisulfonic acid (NDSA) to modulate the orientation of transition dipole moments (TDMs) of the originally isotropic emissive layers composed of cubic perovskite nanoparticles (NCs). Incorporation of the NDSA significantly enhanced the long-range packing order of NCs, leading to an increase in the proportion of horizontal TDMs in the NCs film from 60% to 70%. This improved orientation was instrumental in enhancing light outcoupling efficiency ( out) from 16.15% to 20.09%. As a result, devices with NDSA modified exhibit a peak external quantum efficiency (EQE) of 22.63% at 5,127 cd/m² and a maximum luminance of 13,950 cd/m², significantly outperforming the pristine device. EQE remains above 20% across 400-8,000 cd/m², and device lifetime improves by 400%.In Submission (2025. 09. 03)In Revision (2025. 11. 24)doi.org/10.1002/adma.202517210
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  (192)_[2026] "A 3D-printed flexible microsupercapacitor with advanced electrode structure and plasma surface functionalization for miniaturized energy-storage applications" A.-H. Noh, M.M. Ovhal, D. Srinivasan, J.-W. Kang*, Chem. Eng. J, 527, 171774 (2026)

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  2025.04.23

  Highlights 3D MSCs were manufactured using a single-flow 3D-DIW printing process. Thickness-capacitance trade-off addressed by novel CAC 3D electrodes. Novel CAC 3D electrode enhances charge adsorption and transport kinetics. 9CAC 3D MSCs achieves Ca of 48.6 mF/cm2 and Ea of 3.25 Wh/cm2. High performance 3D MSCs are suitable for miniaturized energy storage applications.AbstractThree-dimensional (3D) microsupercapacitors (MSCs) are miniaturized energy-storage devices characterized by short charge discharge cycles, high power densities, and low environmental impact. However, their low capacitance remains a critical limitation due to the poor conductivity and limited specific surface area (SSA) of conventional electrode materials. Here, we present a strategy combining 3D printing with advanced interdigitated electrode architectures and plasma surface functionalization to enhance electrochemical performance. Plasma treatment of carbon black (CB)-based 3D MSC electrodes using O₂ + CF₄ gases increased the SSA by 255 % and root-mean-square roughness by 310 %. The formation of surface CO and CF bonds enhanced electrolyte/ion adsorption, yielding an areal capacitance (Cₐ) of 6.73 mF/cm2, significantly higher than that of pristine MSCs (2.11 mF/cm2) at 60 A/cm2. Incorporation of silver current collectors within advanced CB/Ag/CB 3D electrodes further improved Cₐ by 7-fold, achieving 48.6 mF/cm2 and a volumetric capacitance of 5.45 F/cm3, with an energy density of 3.25 Wh/cm2. The flexible 3D MSC module (3 series 3 parallel 3D MSCs) demonstrated excellent mechanical and electrochemical stability, highlighting its potential for wearable electronics and miniaturized Internet-of-Things devices.In Revision (2025. 09. 26)In Accept (2025. 12. 10)https://doi.org/10.1016/j.cej.2025.171774
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  (191)_[2025] "Efficient Thermally-Evaporated Near-Infrared Perovskite Light-Emitting Diodes via Phase Regulation" S. He, L. Qin, Z. Liu*, J.-W. Kang, J. Luo*, J. Du* Nano-Macro Letters, 17, 270 (2025)

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  2025.04.23

  Highlights -phase formamidinium lead triiodide (FAPbI3) was prepared based on triple-source co-evaporation.A partial Cs-doping in the FAPbI3 can help with the suppression of the non-radiative recombination, elimination of the metallic Pb, improvement of spatial confinement.Near-infrared perovskite light-emitting diodes (NIR-PeLEDs) based on triple-source co-evaporated FACsPbI3 thin films achieved a maximum external quantum efficiency of 10.25%, which was around 6 times higher than that of FAPbI3-based NIR-PeLEDs. Abstract -phase formamidinium lead triiodide (FAPbI3) has demonstrated extraordinary properties for near-infrared perovskite light-emitting diodes (NIR-PeLEDs). The vacuum processing technique has recently received increasing attention from industry and academia due to its solvent-free feature and compatibility with large-scale production. Nevertheless, vacuum-deposited NIR-PeLEDs have been less studied, and their efficiencies lag far behind those of solution-based PeLEDs as it is still challenging to prepare pure -FAPbI3 by the thermal evaporation. Herein, we report a Cs-containing triple-source co-evaporation approach to develop the perovskite films. The addition of thermally stable Cs cation fills in the perovskite crystal lattice and eliminates the formation of metallic Pb caused by the degradation of FA cation during the evaporation process. The tri-source co-evaporation strategy significantly promotes the phase transition from yellow -phase FAPbI3 to black -phase FACsPbI3, fostering smooth, uniform, and pinhole-free perovskite films with higher crystallinity and fewer defects. On this basis, the resulting NIR-PeLED based on FACsPbI3 yields a maximum EQE of 10.25%, which is around sixfold higher than that of FAPbI3-based PeLEDs. Our work demonstrates a reliable and effective strategy to achieve -FAPbI3 via thermal evaporation and paves the pathway toward highly efficient perovskite optoelectronic devices for future commercialization.Published: 22 May 2025https://link.springer.com/article/10.1007/s40820-025-01776-3
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  (190)_[2025] "Green Solvent Enabled Perovskite Ink for Ambient-Air-Processed Efficient Inkjet-Printed Perovskite Solar Cells" V.V. Satale, S. Chowdhury, A. Mohamed, D.-H. Kim, S. Cho, J.-S. Lee, and J.-W. Kang* Advanced Functional Materials, 35, 2503717 (2025)

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  2025.02.27

  AbstractPerovskite ink based on a green or non-toxic solvent meets industrial requirements for efficient perovskite solar cells (PSCs). Perovskite inks must be developed with non-toxic or involve the limited use of toxic solvents to fabricate efficient inkjet-printed (IJP) perovskite photovoltaics. Herein, -valerolactone is used as a solvent with a low environmental impact, and the strategy showed category 3 toxicity, even with a small quantity of toxic solvents employed to dissolve the perovskite salts. The structural, optical, and electronic properties of IJP perovskite films are improved by adding 1,3-dimethyl-2-imidazolidinone (DMI) to the green perovskite ink. The IJP perovskite films developed by green solvents with 15% (volume %) of DMI exhibited high thickness uniformity ( 97%), and thicker and smoother surfaces than their counterparts. An additive-modified IJP-PSC device achieved a maximum power conversion efficiency (PCE) of 17.78%, higher than that of an unmodified device (14.75%). The performance of the IJP-PSC device is superior primarily because of its exceptional film-thickness homogeneity, larger grains, and appropriate structures. These attributes significantly decreased unwanted reactions of the perovskite with solvents, ensuring phase purity and enhancing overall efficiency. The innovative green-solvent ink-engineering strategy for producing large-scale perovskite films shows great promise for advancing perovskite solar module technology (with PCE of 13.14%).Published October 1, 2025https://doi.org/10.1002/adfm.202503717
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  (189)_[2025] "Highly Efficient 3D-Printed PVDF-based Triboelectric Nanogenerators featuring Polymorphic Perovskite Nanofillers"N.H.Z Karimy, H. LI, H.B. Lee, D.P. Ojha, M.M. Ovhal, V. Devaraj, S. Lim* and J.-W. Kang* Advanced Functional Materials, 35, 2424271 (2025)

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  2025.02.27

  AbstractThe realization of optimal performance in polyvinylidene fluoride (PVDF)-based triboelectric nanogenerators (TENGs) is fundamentally linked to the enhancement of the -phase content of PVDF ( -PVDF), which is crucial for improving dielectric properties and surface charge density. Among various strategies, the incorporation of semiconducting perovskite nanofillers has been particularly effective in achieving the desired -PVDF phase for TENG applications. Herein, PVDF dielectric films are embedded with polymorphic formamidinium lead triiodide (FAPbI3) perovskite nanofillers and fabricated using a cost-effective 3D direct-ink writing setup. The phase transformation of FAPbI3 nanofillers within the PVDF matrix, in response to varying annealing temperatures, resulted in the formation of PVDF-FAPbI3( ) and PVDF-FAPbI3( ) composite films, each exhibiting distinct morphology and dielectric characteristics. The incorporation of -FAPbI3 nanofillers rendered the composite film porous and increased the -PVDF content from 45% to 83%. By converting the -FAPbI3 into the -FAPbI3 through post-annealing, the composite film transitioned into a mesoporous structure with enhanced tribo-positive properties. This modification substantially improved the output performance of the TENG, achieving a peak-to-peak voltage (Vp-p) of 392 Vand a power density of 2587 W cm 2. This work highlights the significant impact of perovskite polymorphism on the performance of TENG devices. Published : September 25, 2025 https://doi.org/10.1002/adfm.202424271
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  (188)_[2024] "Perovskite nanocrystals passivated by aromatic phosphonic acid for high-performance light-emitting diodes" M. I. Saleem, S. He, S.H. Kim, J.-W. Kang* and J.-H. Lee* Journal of Materials Chemistry C, 12, 17289 (2024)

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  2024.10.25

  AbstractOptimizing the content of inherent capping ligands in perovskite nanocrystals (PeNCs) is a crucial strategy for enhancing the performance and stability of perovskite light-emitting diodes (PeLEDs). However, the highly dynamic adsorption desorption state of capping ligands and their detachment from the surface of PeNCs often result in degraded optical properties and the emergence of surface defects. In this study, we investigated the use of benzylphosphonic acid (BPA), an aromatic conductive molecule, for passivation to replace the native capping ligands of FAPbBr3 NCs. Comprehensive characterization results validate that the original long insulative ligands were partially substituted with short conductive phosphine oxide functional groups, effectively passivating the nonradiative defects of FAPbBr3 while enhancing electron injection into perovskite emitting layers. Moreover, this proposed ligand-exchange strategy significantly improved the photoluminescence quantum yield of FAPbBr3 NCs. Consequently, we achieved a high-performance PeLED with an external quantum efficiency of 12.9% at 4660 cd m 2 using BPA-passivated FAPbBr3 NCs. These findings underscore the potential of post-passivated PeNCs via aromatic acid in fabricating high-performance optoelectronic devices.DOIhttps://doi.org/10.1039/D4TC02419B
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  (187)_[2024] "Efficient deep-blue electroluminescence from Ce-based metal halide" L. Yang, H. Du, J. Li, Y. Luo, X. Lin, J. Pang, Y. Liu, L. Gao, S. He, J.-W. Kang, W. Liang, H. Song, J. Luo, J. Tang, Nature Communication, 15, 6240 (2024)

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  2024.09.04

  AbstractRare earth ions with d-f transitions (Ce3+, Eu2+) have emerged as promising candidates for electroluminescence applications due to their abundant emission spectra, high light conversion efficiency, and excellent stability. However, directly injecting charge into 4f orbitals remains a significant challenge, resulting in unsatisfied external quantum efficiency and high operating voltage in rare earth light-emitting diodes. Herein, we propose a scheme to solve the difficulty by utilizing the energy transfer process. X-ray photoelectron spectroscopy and transient absorption spectra suggest that the Cs3CeI6 luminescence process is primarily driven by the energy transfer from the I2-based self-trapped exciton to the Ce-based Frenkel exciton. Furthermore, energy transfer efficiency is largely improved by enhancing the spectra overlap between the self-trapped exciton emission and the Ce-based Frenkel exciton excitation. When implemented as an active layer in light-emitting diodes, they show the maximum brightness and external quantum efficiency of 1073 cd m 2 and 7.9%, respectively.Published: 24 July 2024https://www.nature.com/articles/s41467-024-50508-5
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  (186)_[2025] "High-Performance perovskite quantum dots light-emitting diodes with hole transport layer engineering and synergetic outcoupling enhancement" S. He, W. Zhou, S. Ham, K.-J. Ko, J. Luo, B.-J. Lee, H.B. Lee*, J.-H. Lee* and J.-W. Kang* Applied Surface Science, 680, 161384 (2025)

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  2024.06.03

  Highlights Device engineering is used to enhance the charge injection and out of PeQLEDs. The lower n of mPEDOT:PSS benefits the light extraction from PeQLEDs. The bilayer mPEDOT:PSS-PVK shields the QDs from decomposition. The out of the PeQLEDs is enhanced by tailoring the thickness of ITO.AbstractPerovskite quantum dot light-emitting diodes (PeQLEDs) are frequently considered as the most promising alternatives to organic light-emitting diodes (OLEDs). However, the efficiency of PeQLEDs remains inferior to OLEDs due to suboptimal charge carrier transport and intrinsic light outcoupling efficiency ( out). Herein, a combination of hole transport layer (HTL) engineering and substrate engineering is demonstrated to improve the charge injection and out of PeQLEDs. To replace the conventional PEDOT:PSS, a novel HTL bilayer based on modified PEDOT:PSS and PVK with a lower refractive index and fewer trap densities at the HTL-QDs interface is developed. Additionally, this study identifies the ideal thickness of ITO for achieving optimal out of PeQLEDs through optical simulations and experimental validation. Based on the synergistic use of HTL bilayer and 70-nm-thick ITO, the PeQLEDs achieved an optimal external quantum efficiency of 17.96 % at a luminance of 1763 cd/m 2 and 15.19 % at 8300 cd/m 2 without using any external outcoupling structure, indicating a low efficiency roll-off.Graphical abstractTwo complementary strategies, i.e. hole transport layer (HTL) engineering and substrate engineering are developed to enhance the charge injection and light outcoupling efficiency of PeQLEDs. With the incorporation of mPEDOT:PSS-PVK and 70-nm-thick ITO, the PeQLED device achieved an EQE of 17.96% at a brightness of 1763cd/m 2 with low efficiency roll-off.https://doi.org/10.1016/j.apsusc.2024.161384
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  (185)_[2024] "Novel Strategy towards Efficiency Enhancement of Flexible Optoelectronic Devices with Engineered M13 Bacteriophage" J.H. Kim, G. Kim, S.-J. Kim, Y.B. Kim, J.-W. Kang, J.W. Choi,* J.-W. Oh* and M. Song* Small Structure, 5, 2400007 (2024)

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  2024.06.03

  AbstractPlasmonic nanostructures, which exhibit notable localized surface plasmon resonance (LSPR) properties, are a promising approach for improving the efficiency of fiber-shaped dye-sensitized solar cells (FDSSCs) and flexible organic light-emitting diodes (FOLEDs). Herein, novel plasmonic nanostructure is successfully synthesized via the self-densification of gold nanoparticles (Au NPs) onto a genetically engineered M13 bacteriophage template. The synthesized Au NP-M13 bio-nanostructure show extraordinary gap-plasmon effects and significantly enhanced LSPR properties compared to randomly dispersed Au NPs for both solid-state FDSSCs (SS-FDSSCs) and FOLEDs. Briefly, a power conversion efficiency (PCE) increment of 40.7% is recorded for the Au metallic NPs-anchored M13 bacteriophage (Au NPs-M13) enhanced SS-FDSSCs; whereas an external quantum efficiency (EQE) increment of 47.2% is achieved for the Au NPs-M13 enhanced FOLEDs.https://doi.org/10.1002/sstr.202400007
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  (184)_[2024] "Indium-free, highly flexible semi-transparent organic light-emitting diodes featuring MoO3/Au/MoO3 multilayer anode and cathode" K.-J. Ko*, H.W. Cho, H.B. Lee, P.J. Jesuraj, J.-W. Kang*, S.Y. Ryu* Organic Electronics, 128, 107022 (2024)

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  2024.03.06

  Highlights Flexible transparent OLEDs (Tr-OLEDs) with inverted architecture demonstrated. MoO3/Au/MoO3 electrodes employed as top/bottom electrodes with 76% transmittance. The efficiencies flexible Tr-OLEDs are similar to that of conventional ITO devices. High mechanical robustness and stable performance attained with 1 mm bending radius. MAM electrode can replace ITO for large-area flexible optoelectronic applications.AbstractOrganic light-emitting diodes (OLEDs) typically exhibit a high contrast ratio, wide viewing angles, and low power consumption, enabling their widespread use in display and lighting applications. More recently, transparent OLEDs (Tr-OLEDs) that offer design versatility, seamless integration with the environment, and a minimized obstruction of the view have been developed and applied in various fields including display devices. Here, we report the fabrication of solution-processed, flexible Tr-OLEDs with an inverted device architecture. To ensure the high transparency of the Tr-OLEDs, oxide/metal/oxide (OMO)-structured electrodes, namely MoO3/Au/MoO3 (MAM), were used as both the transparent cathode and anode. The MAM electrodes exhibited a transmittance of 76% at a wavelength of 550 nm and a low sheet resistance of 15 ohm/sq. Moreover, the as-fabricated flexible Tr-OLEDs exhibited efficiency comparable to that of the bottom-emitting OLEDs with MAM and silver electrodes, thus proving the excellent charge carrier-to-light conversion within the device. Additionally, the flexible Tr-OLEDs were mechanically robust and exhibited excellent performance retention even up to a bending radius of 1 mm. Our findings suggest that MAM electrodes can be replace indium-doped tin oxide (ITO) for applications in large-area flexible transparent display and lighting.https://doi.org/10.1016/j.orgel.2024.107022
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  (183)_[2024] "Ink engineering using 1,3-dimethyl-2-imidazolidinone solvent for efficient inkjet-printed triple-cationic perovskite solar cells" V.V. Satale, H.B. Lee, B. Tyagi, M.M. Ovhal, S. Chowdhury, A. Mohamed, D.-H. Kim and J.-W. Kang* Chemical Engineering Journal, 493, 152541 (2024)

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  2024.02.18

  Highlights Perovskite films were fabricated using a scalable inkjet printing (IJP) technique. 1,3-dimethyl-2-imidazolidinone (DMI) high boiling solvent used in perovskite ink. DMI-based IJP perovskite has a uniform, smoother film with large grains surface. IJP perovskite has a more suitable energy band alignment with SnO2 and Spiro-OMeTAD. The champion device achieved a PCE of 17.5 % and module PCE of 11.4 % (A = 12.3 cm2).AbstractInk engineering increases the quality and uniformity of large-scale perovskite films for efficient inkjet-printed perovskite solar cells (IJP-PSCs). The absorber layer in PSCs must be pinhole- and crack-free, highly uniform, with minimum defects, and have better optoelectronic properties, to improve PSC device performance. Herein, a different strategy, such as solvents with high boiling points (BPs), is used to modify the perovskite inks to obtain uniform and better-quality IJP-perovskite films. The perovskite film prepared with a 1,3-dimethyl-2-imidazolidinone (DMI) solvent is highly uniform ( 96 %), thicker, with a smoother surface, and contains bigger grains than -butyrolactone (GBL) based IJP-perovskites. The DMI solvent-based IJP-PSC device shows a greater than 17.5 % power conversion efficiency (PCE), which is much higher than that possible with GBL-based devices (PCE 13.8 %). The better performance of the IJP-PSC device is mainly due to the film s uniformity, large grains, and well-formed structures, which reduce the occurrence of specific chemical reactions within the perovskite material. The presented ink engineering strategy to develop highly uniform IJP perovskite films has the potential to be applied to perovskite solar modules.Graphical abstractA high boiling point solvent is used to engineer the perovskite ink for efficient, stable inkjet-printed perovskite solar cell (IJP-PSC) devices. The 1,3-dimethyl-2-imidazolidinone (DMI) solvent-based ink exhibited a highly uniform and smoother film, creating larger grains that resulted in efficient charge transfer to electron or hole transport layers. The DMI solvent-based IJP-PSC device showed an impressive power conversion efficiency of 17.50%, with better stability proving its potential for the scalable fabrication of inkjet-printed PSCs.https://doi.org/10.1016/j.cej.2024.152541
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  (182)_[2025] "Low-Cost, Scalable Fabrication of Multi-Dimensional Perovskite Solar Cells and Modules Assisted by Mechanical Scribing" H.B. Lee, A. Mohamed, N. Kumar, N.H.Z. Karimy, V.V. Satale, B. Tyagi, D.-H. Kim and J.-W. Kang* Small Methods, 9, 2400850 (2025)

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  2024.02.18

  AbstractThe performance and scalability of perovskite solar cells (PSCs) based on 3D formamidinium lead triiodide (FAPbI3) absorber are often hindered by defects at the surface and grain boundaries of the perovskite. To address this, the study demonstrates the use of pyrrolidinium iodide for the in situ formation of an energetically aligned 1D pyrrolidinium lead triiodide (PyPbI3) capping layer over the 3D FAbI3 perovskite. The thermodynamically stable PyPbI3 perovskitoids, formed through cation exchange reactions, effectively reduce surface and grain boundary defects in the FAPbI3 perovskite. In addition to improved phase stability, the resulting 1D/3D perovskite film forms a cascade energy band alignment with the other functional layers in PSCs, enabling a barrier-free interfacial charge transport. With a maximum power conversion efficiency (PCE) of 23.1% and 20.7% at active areas of 0.09 and 1.05 cm2, respectively, the 1D/3D PSCs demonstrate excellent performance and scalability. Leveraging this improved scalability, the study has successfully developed a mechanically-scribed 1D/3D perovskite mini-module with an unprecedentedly high PCE of 20.6% and a total power output of 270 mW at an active area of 13.0 cm2. The 1D/3D multi-dimensional perovskite film developed herein holds great promise for producing low-cost, high-performance perovskite photovoltaics at both the cell and module levels. https://doi.org/10.1002/smtd.202400850
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  (181)_[2024] “ NiCo2O4 Nanoneedle-Coated 3D Reticulated Vitreous Porous Carbon Foam for High-Performance All-Solid-State Supercapacitors” K. Yadav, M. M. Ovhal, S. Parmar, N. Gaikwad, S. Datar, J.-W. Kang, and T. U. Patro* ACS Appl. Nano Mater. 7, 2312–2324 (2024)

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  2024.02.15

  A binder-free, electrically conducting nickel cobalt oxide (NiCo2O4)-reticulated vitreous carbon (RVC) foam (NiCo2O4@RVC) electrode was prepared by template carbonization of open-cell polyurethane foam followed by the hydrothermal growth of NiCo2O4 nanoneedles, leading to the formation of a hierarchical porous electrode. The growth of NiCo2O4 nanoneedles (length and diameter) on RVC foam was found to depend on hydrothermal coating time, which varied between 6 and 12 h. However, optimally grown NiCo2O4 nanoneedles for 8 h on an RVC foam with an average diameter of 77( 9) nm and length of 2 m exhibited the lowest charge-transfer resistance, resulting in the areal capacitance (Ca) of 2.45 F/cm2 at a scan rate of 5 mV/s. A symmetric supercapacitor (SC) device exhibited a maximum Ca of 1.22 F/cm2 at a current density of 1 mA/cm2 and an energy density of 2.51 W h/kg at a power density of 30 W/kg. The SCs showed a capacitance retention of 97% after 10,000 galvanostatic charge/discharge (GCD) cycles, apparently due to a highly stable NiCo2O4 structure on the RVC network structure, which was ascertained by various characterization techniques after the GCD cycles. Further, the SC module, comprising three devices in series, successfully lights up an LED, demonstrating the energy storage capability of these electrodes in real applications. Owing to its excellent electrochemical performance, the NiCo2O4@RVC electrode offers a low-cost and efficient alternative material in energy storage applications.Received4 December 2023Published inissue 26 January 2024https://doi.org/10.1021/acsanm.3c05812
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  (180)_[2024] “ Filamentous Virus-Templated Nickel Hydroxide Nanoplates as Novel Electrochemical Pseudocapacitor Materials” M.M. Ovhal, H.B. Lee, N. Kumar, J.-W. Oh and J.-W. Kang* Polymer Korea. 48, 234-241 (2024).

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  2024.02.15

  Pseudocapacitive metal hydroxide nanostructures are promising active electrode materials for supercapacitor applications. Here, we demonstrate the in-situ growth of nickel hydroxide (Ni(OH)2) nanostructures on filamentous M13 bacteriophage template. The M13-Ni(OH)2 bio-nanostructure exhibits a fibrous morphology and a preferential growth orientation along the (001) crystal plane. Interestingly, the M13-Ni(OH)2 electrode demonstrates superior electrochemical properties. The areal capacitance (Ca) of M13-Ni(OH)2 and Ni(OH)2 electrodes was 18 mF/cm2 and 14 mF/cm2, respectively, indicating a 28% increase. The improved electrochemical performance is due to increased surface roughness, enhanced charge adsorption/desorption sites, and reduced charge transfer resistance. This also contributed to an 18% increase in cyclic stability compared to the Ni(OH)2 electrode analogue. Overall, this work successfully shows the use of a bio-template to control the growth of novel metal-oxide nanostructures for energy storage applications.Received December 18, 2023;http://journal.polymer-korea.or.kr/journal/archive/view/4442
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  (179)_[2024] “One-meter-long, All-3D-printed Supercapacitor Fibers based on Structurally Engineered Electrode for Wearable Energy Storage” M.M. Ovhal, H.B. Lee, V.V. Satale, B. Tyagi, N. Kumar, S. Chowdhury and J.-W. Kang* Adv. Energy Mater. 14, 2303053 (2024)

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  2023.12.26

  AbstractFiber-shaped energy storage devices have great potential for use as an intelligent power source for futuristic wearable technology. To produce high-performance fiber-shaped energy storage devices, a thin fiber material with a high energy density, shape adaptability, and longevity is critical. Herein, 3D fiber-shaped supercapacitors (SCs) comprising MXene-PEDOT:PSS active electrodes made using the 3D-direct-ink-writing (DIW) technique are demonstrated. Embedding a silver (Ag) current collector in the active electrode facilitated faster charge transport in the fiber-shaped 3D-SCs, enabling them to create a unique 3D-electrode structure that solves the thickness and length problem of electrode-dependent capacitance in fiber-shaped devices. At one-meter long, the fully-printed fiber-shaped 3D-SC exhibits a low charge transfer resistance that leads to the high areal capacitance of 1.062 F cm 2 and gravimetric capacitance of 185.9 F g 1, with a high areal energy density of 94.41 Wh cm 2 at a power density of 1,142 W cm 2. The fiber-shaped 3D-SCs also exhibit excellent electrochemical and mechanical stability at different temperatures in air and water. With their unique electrode structure and uninterrupted power supply, these R2R 3D-DIW printed fiber-shaped SCs can boost the development of innovative textile technology.https://doi.org/10.1002/aenm.202303053
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  (178)_[2023] “Three-dimensional polymer-nanoparticle-liquid ternary composite for ultrahigh augmentation of piezoelectric nanogenerators” Hai Li, Hock Beng Lee, Jae-Wook Kang, Sooman Lim* Nano Energy, 113, 108576 (2023).

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  2023.06.28

  Highlights A novel polymer-nanoparticle-liquid ternary composite based piezoelectric nanogenerator is developed. PFOES liquid nanodroplets, BTO NPs, and PVDF polymer have collectively formed a stable composite with a 3D scaffold. The ternary composite exhibits a remarkably improved stress transfer ability and enhanced energy harvesting output. This PNL-PENG device can function as a tactile perception tool.AbstractThe development of flexible nanogenerators that can convert passively generated environmental energy into electricity is crucial for sustainable energy generation. Herein, we rationally designed a polymer-nanoparticle-liquid (PNL) ternary composite, comprising polydopamine-modified barium titanate nanoparticles (PDA-BTO NPs) doped polyvinylidene fluoride (PVDF), and 1H,1H,2H,2H-perfluorodecyltriethoxysilane (PFOES) liquid nanodroplets, for application in piezoelectric nanogenerators (PENGs). The inter-discrete PFOES nanodroplets enabled the formation of a three-dimensional (3D) scaffold matrix in the ternary composite, which is highly beneficial for the stress transfer of PENGs. Finite-element analysis revealed that the ternary composite had a remarkably improved stress transfer ability due to the incorporation of highly deformable PFOES liquid nanodroplets, which increased the net stress exerted on PDA-BTO NPs and the PVDF matrix. The PNL composite-based PENG (PNL-PENG) device exhibited an enhanced piezoelectric performance, achieving an output voltage, current, and power density of 102 V, 10 A, and 70 W/cm2, respectively, which are record-high results compared to those achieved by binary composite-based PENGs. Moreover, the PNL-PENG also demonstrated tremendous potential to function as a highly sensitive tactile perception tool for shape recognition. The concept of PNL-PENG devices represents a milestone in the domain of human-machine interaction, taking a significant step toward the advancement of flexible and wearable electronics.https://www.sciencedirect.com/science/article/pii/S2211285523004135Published 2023. 08. 01
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  (177)_[2023] "Fluorinated Organic A-Cation Enabling High-Performance Hysteresis-Free 2D/3D Hybrid Tin Perovskite Transistor" W. Yang, G. Park, A. Liu, H.B. Lee, J.-W. Kang*, H. Zhu* and Y.-Y. Noh* Adv. Funct. Mater. 33, 2303309 (2023)

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  2023.05.02

  Two-dimensional (2D) tin-based perovskites have gained considerable attention for use in diverse optoelectronic applications, such as solar cells, lasers, and thin-film transistors (TFTs), owing to their good stability and optoelectronic properties. However, their intrinsic charge-transport properties are limited and the insulating bulky organic ligands hinder the achievement of high-mobility electronics. Blending three-dimensional (3D) counterparts into 2D perovskites to form 2D/3D hybrid structures is a synergistic approach that combines the high mobility and stability of 3D and 2D perovskites, respectively. In this study, a reliable p-channel 2D/3D tin-based hybrid perovskite TFTs comprising 3D formamidinium tin iodide (FASnI3) and 2D fluorinated 4-fluoro-phenethylammonium tin iodide ((4-FPEA)2SnI4) are reported. The optimized FPEA-incorporated TFTs show a high hole mobility of 12 cm2 V-1 s-1, an on/off current ratio of over 108, and a subthreshold swing of 0.09 V dec-1 with negligible hysteresis. This excellent p-type characteristic is compatible with n-type metal-oxide TFT for constructing complementary electronics. Two procedures of antisolvent engineering and device patterning are further proposed to address the key concern of low performance reproducibility of perovskite TFTs. This study provides an alternative A-cation engineering method for achieving high-performance and reliable tin-halide perovskite electronics.https://doi.org/10.1002/adfm.202303309Publish : September 5, 2023
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  (176)_[2023] "Spray-Assisted Deposition of SnO2 Electron Transport Bilayer for Efficient Inkjet-Printed Perovskite Solar Cells" V.V. Satale, N. Kumar, H.B. Lee, M.M. Ovhal, S. Chowdhury, B. Tyagi, A. Mohamed, and J.-W. Kang* Inorganic Chemistry Frontier. 10, 3558–3567 (2023)

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  2023.04.10

  Developing an efficient electron transport layer (ETL) through structural modification is essential to produce high-performance perovskite solar cell (PSC) devices. Specifically, the ETL should exhibit low defects, high optical transparency, and charge selectivity for ideal electron transport. Herein, we demonstrate (i) the low-temperature fabrication of tin oxide (SnO2) ETLs with a bilayer structure, and (ii) inkjet-printing of triple-cation perovskite film. Through the combined use of spin-coating and spray deposition, the optimized SnO2-bilayer ETL shows a nano-granule-textured surface, noticeably lesser defects, and cascade conduction band position with the inkjet-printed (IJP) perovskite. The champion IJP PSC device, based on the SnO2-bilayer ETL recorded an outstanding power conversion efficiency (PCE) of ~16.9%, which is significantly higher than the device based on the conventional SnO2 ETL (PCE ~14.8%). The improved photovoltaic performance of the SnO2-bilayer-based PSC arises mainly from more efficient charge transport and suppressed recombination at the ETL/perovskite interface. The SnO2-bilayer ETL and IJP-perovskite films demonstrated herein can be potentially used for large-scale manufacturing of PSC modules.Submission: 2023.03.31Publicaion: 2023. 06. 21DOIhttps://doi.org/10.1039/D3QI00599B
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  (175)_[2023] "Optical Engineering of FAPbBr3 Nanocrystals via Conjugated Ligands for Light-Outcoupling Enhancement in Perovskite Light-Emitting Diodes" S. He, H.B. Lee, K.-J. Ko, N. Kumar, J.-H. Jang, S.-O. Cho, M. Song, W. Zhou, B.-J. Lee, J.-H. Lee* and J.-W. Kang* Adv. Opt. Mater. 11, 2300486 (2023)

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  2023.02.28

  Formamidinium lead bromide (FAPbBr3) nanocrystals (NCs) that exhibit ultra-pure green emission are the most promising candidates for future displays. Despite the rapid development of light-emitting diodes (LEDs) based on perovskite NCs (PeNCs), there is limited research detailing their intrinsic light outcoupling. Herein, we propose the use of a short-chain fluoroaromatic ligand, 4-fluoro-phenethylammonium bromide (FPEABr) via a facile spin-casting method to fine-tune the refractive index (n) and horizontal dipole ratio values of the perovskite emitter layer and simultaneously suppress the defects formed during film deposition. After FPEABr ligand exchange, the FAPbBr3 NCs films exhibite a refractive index n significantly lower (by about 0.4) than bulk (2D/quasi 2D or 3D) perovskite films and show an enhanced value of 77%. Therefore, we successfully produce ultra-pure green PeLEDs with a maximum current efficiency of ~ 50 cd A-1, a maximum luminance of 21304 cd m-2, and a peak external quantum efficiency of 11.33% at a high luminance of 2804 cd m-2, approaching the theoretical value of 11.90% given the structure, photoluminance quantum yield, and horizontal dipole ratio. https://doi.org/10.1002/adom.202300486Cover Image : https://onlinelibrary.wiley.com/doi/10.1002/adom.202370066
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  (174)_[2024] “Development of high efficiency, spray-coated perovskite solar cells and modules using additive-engineered porous PbI2 films” B. Tyagi, N. Kumar, H.B. Lee, M.M. Ovhal, V.V. Satale, A. Mohamed, D.-H. Kim and J.-W. Kang* Small Method,8, 2300237 (2024)

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  2023.02.28

  Small MethodsResearch ArticleDevelopment of High Efficiency, Spray-Coated Perovskite Solar Cells and Modules Using Additive-Engineered Porous PbI2 FilmsBarkha Tyagi, Neetesh Kumar, Hock Beng Lee, Manoj Mayaji Ovhal, Vinayak Vitthal Satale, Asmaa Mohamed, Do-Hyung Kim, Jae-Wook KangFirst published: 25 May 2023 https://doi.org/10.1002/smtd.202300237Citations: 2 Abstract The development of anti-solvent free, scalable, and printable perovskite film is crucial to realizing the low-cost roll-to-roll development of perovskite solar cells (PSCs). Herein, large-area perovskite film fabrication is explored using a spray-assisted sequential deposition technique. How propylene carbonate (PC) solvent additive affects the transformation of lead halide (PbI2) into perovskite at room temperature is investigated. The result shows that PC-modified perovskite films exhibit a uniform, pinhole-free morphology with oriented grains compared with pristine perovskite films. The PC-modified perovskite film also has a prolonged fluorescence lifetime that indicates lower carrier recombination. The champion PSC devices based on PC-modified perovskite film realize a power conversion efficiency (PCE) of 20.5% and 19.3% at an active area (A) of 0.09 cm2 and 1 cm2, respectively. The fabricated PSCs are stable and demonstrate 85% PCE retention following 60 days of exposure to ambient conditions. Furthermore, perovskite solar modules (A 13 cm2) that yield a PCE of 15.8% are fabricated. These results are among the best reported for the state-of-art spray-coated PSCs. Spray deposition coupled with a PC additive is highly promising for economical and high-output preparation of PSCs.- Submission (2023.2.24). https://doi.org/10.1002/smtd.202300237
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  (173)_[2023] “Spray deposited, virus-templated SnO2 mesoporous electron transport layer boosting the performance of perovskite solar cells” N. Kumar, H.B. Lee, B. Tyagi, M.M. Ovhal, S. Cho, J.-S. Lee, J.-W. Oh, J.-W. Kang* Solar RRL, 7, 2300065 (2023)

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  2022.11.14

  In recent years, researchers have developed spray deposition technology to fabricate tin oxide (SnO2) electron transport layer (ETL) with the aim of manufacturing high-efficiency, large-area perovskite solar cell (PSC). However, the power conversion efficiency (PCE) of PSC based on sprayed SnO2 ETL remains inferior to that of the spin-coated SnO2 ETL. Herein, we demonstrate the combined use of spray deposition and genetically-engineered M13 bacteriophages to fabricate M13-SnO2 biohybrid ETL for PSC application. The spray-deposited M13-SnO2 ETLs exhibited mesoporous morphologies with 85% transmittance in UV-vis region. Though the use of M13-SnO2 ETL, the sequential-deposited PSCs achieved a maximum PCE of ~22.1%. The improved performance of the PSC is attributable to the mesoporous morphology of M13-SnO2 ETL that facilitated the phase conversion of PbI2 into perovskite. When sprayed on large area (~62 cm2) substrates, the M13-SnO2 based PSCs displayed a highly consistent PCE, demonstrating the excellent scalability of spraying process. Furthermore, M13-SnO2-based PSCs exhibited higher ambient stability compared to the SnO2-based PSCs.- Submission (2023.1.30). https://doi.org/10.1002/solr.202300065
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  (172)_[2023] “Compact-Porous Hole-Transport-Layer for Highly Efficient Near-Infrared Region Transparent Perovskite Solar Cells for Tandem Applications” B. Tyagi, N. Kumar, H.B. Lee, Y.M. Song, S. Cho, J. -S. Lee, J.-W. Kang* J. Alloys Compounds, 960, 170970 (2023) .

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  2022.11.14

  Highlights ● The cp-NiOx films were consecutively fabricated using spin-coating and spray-coating techniques.● The cp-NiOx/perovskite interface possesses lower buried defects.● The cp-NiOx films have mesoporous surface morphology and excellent surface properties for perovskite film formation.● Wide-bandgap perovskite solar cell consisting cp-NiOx HTL yielded PCE of 15.95 % and NIR transmittance ( 92 %).● 4T perovskite/silicon tandem cells based on the cp-NiOx HTL yielded a PCE of 26.0 % with superior stability.AbstractWide-bandgap perovskites solar cells (PSCs) are vital as top cells in perovskite-based tandem solar cells (TSCs). However, poor band alignment with the charge transport layer and unwanted parasitic absorption in the top semitransparent-PSC (ST-PSC) are major factors limiting the power conversion efficiency (PCE) of TSCs. Herein, we present a compact-porous nickel oxide (cp-NiOx) hole-transport layer (HTL) sequentially fabricated using a sol-gel suspension and colloidal suspension of highly crystalline NiOx. The cp-NiOx film exhibited enhanced transparency, mesoporous surface morphology, and better energy band alignment with a 1.68 eV perovskite film for fabricating highly near-infrared transparent ( 92 % (@800 1200 nm)) ST-PSCs. The best cell achieved a PCE of 15.9 %. In addition, a four-terminal perovskite/silicon TSC based on the cp-NiOx HTL achieved an outstanding PCE of 26.0 %. The tailored energy band structure and reduced parasitic absorption in the near-infrared region of the ST-PSCs based on the cp-NiOx HTL enabled fabrication of highly efficient inverted ST-PSCs for perovskite/silicon TSCs.https://www.sciencedirect.com/science/article/pii/S0925838823022739- Submission (2022. 9. 20)- Revision (2023. 5. 10)- Published (2023.10. 15)
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  (171)_[2023] “Flexible, stripe-patterned organic solar cells and modules based on multilayer-printed Ag fibers for smart textile applications” M.M. Ovhal, H.B. Lee, S. Boud, K.-J. Ko, W.-Y. Jin, N. Kumar, B. Tyagi, J.-W. Kang* Materials Today Energy, 34, 101289 (2023)

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  2022.11.14

  Rapid advancement in the fabrication technologies of stripe/fiber-shaped optoelectronic devices has driven the performance of smart textile electronics to a new height. In the development of high-performance smart textile electronics, ITO-free flexible transparent conductive electrodes (TCEs) are particularly desirable because they offer superior flexibility and lower manufacturing cost than the brittle ITO-based counterparts. Herein, we innovatively combine spin-coating and 3D direct-ink writing (3D-DIW) techniques to develop large-area (5 5 cm2) PEDOT:PSS/Ag-fibers hybrid TCEs (denoted as DIW-TCEs) for application in flexible organic solar cells (OSCs). Through a multilayer printing strategy, high aspect-ratio Ag-fibers are successfully deposited on top of the planar PEDOT:PSS film. The resulting DIW-TCEs, when fully embedded in a colorless polyimide substrate, exhibit excellent electrical conductivity (sheet resistance ~ 4 Ω/□), superior optical transmittance, and mechanical flexibility. One-dimensional stripe-patterned OSCs (stripe-OSCs) based on the DIW-TCE achieved a power conversion efficiency (PCE) of 9.3% and 8.2% at an active area of 0.11 cm2 and 0.31 cm2, respectively. For real-life application, a flexible power module was constructed using eight stripe-OSCs. When attached on textile, the module successfully lit up a commercial LED upon photocharging. The unique DIW-TCE fabricated herein can be the ITO-free alternative for the production of smart textile electronics.June 2023https://doi.org/10.1016/j.mtener.2023.101289
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  (170)_[2023] “Intercalation of Ammonium Cationic Ligands Enabled Grain Surface Passivation in Sequential-Deposited Perovskite Solar Cells” H.B. Lee, N. Kumar, S. Cho, S. Hong, H.H. Lee, H.J. Kim, J.-S. Lee, J.-W. Kang* Adv. Energy & Sustainability Res. 4, 2200128 (2023).

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  2022.11.14

  Solution-processed formamidinium lead iodide (FAPbI3) perovskite typically contains a high number of ionic defects that are intrinsically formed during film formation. To reduce the defects, which undermine the performance and stability of FAPbI3 films, post-synthetic surface passivation treatment is widely practiced. However, the practicality of the surface passivation approach is limited by the poor coverage and incomplete adsorption of passivators into the defective sites. Unprecedentedly, we demonstrate the use of 4-(trifluoromethyl)benzylammonium iodide (CF3BZAI) as a novel passivator additive for sequentially-deposited perovskite films. Due to its unique molecular structure and CF3 moiety, CF3BZAI is expected to have enhanced adsorption with defect sites during the film formation. Owing to grain surface passivation, the CF3BZAI-intercalated FAPbI3 (target) film has enhanced morphology and crystallinity as well as significantly fewer defects than the normal FAPbI3 film. Interestingly, the intercalation of CF3BZAI passivators does not lead to the formation of a low-dimensional perovskite phase in FAPbI3 films. The best perovskite solar cell (PSC) device based on the target film achieved a maximum efficiency of ~22.4%, which is much higher than the efficiency (~20.7%) of the normal device. CF3BZAI-assisted grain surface passivation is a facile yet effective strategy to enhance the performance and stability of FAPbI3-based PSCs.January 2023https://doi.org/10.1002/aesr.202200128