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)