Suppressing phase disproportionation in quasi-2D perovskite light-emitting diodes

Abstract

Electroluminescence efficiencies and stabilities of quasi-two-dimensional halide perovskites are restricted by the formation of multiple-quantum-well structures with broad and uncontrollable phase distributions. Here, we report a ligand design strategy to substantially suppress diffusion-limited phase disproportionation, thereby enabling better phase control. We demonstrate that extending the π-conjugation length and increasing the cross-sectional area of the ligand enables perovskite thin films with dramatically suppressed ion transport, narrowed phase distributions, reduced defect densities, and enhanced radiative recombination efficiencies. Consequently, we achieved efficient and stable deep-red light-emitting diodes with a peak external quantum efficiency of 26.3% (average 22.9% among 70 devices and cross-checked) and a half-life of ~220 and 2.8 h under a constant current density of 0.1 and 12 mA/cm2, respectively. Our devices also exhibit wide wavelength tunability and improved spectral and phase stability compared with existing perovskite light-emitting diodes. These discoveries provide critical insights into the molecular design and crystallization kinetics of low-dimensional perovskite semiconductors for light-emitting devices.

Light-Emitting Organic Semiconductor-Incorporated Perovskites: Fundamental Properties and Device Applications

“…These derivatives were found to effectively regulate n phase separation by suppressing ion migration. 80 As a result, small n phase of 1 or 2 and high n phase of over 8 were almost eliminated (Figure 5A,B). Suppressed ion migration and n phase separation lead to high EQE over 26% at a peak wavelength of 700 nm and enhanced operational stability.…”

“…Very recently, Wang et al designed a series of novel semiconducting LA cations featuring twisted biphenyl moieties with enhanced cross-sectional area and bulkiness. These derivatives were found to effectively regulate n phase separation by suppressing ion migration . As a result, small n phase of 1 or 2 and high n phase of over 8 were almost eliminated (Figure A,B).…”

“…(H) PL spectra with and without an emissive organic dopant, Coumarin 153 as the energy acceptor in a perovskite host . (A and B) Reproduced with permission from ref . Copyright 2023 Springer Nature.…”

“…3,67−71 In another example, the emission wavelength of quasi-2D PeLED can be well-controlled with PBA perovskite with increasing bulkiness from left to right; their capability to control n phase distribution and suppress high n phase perovskites after thermal annealing is characterized by absorption spectra and shown in panel B. 80 (C) A scheme of 2D perovskite lattice using BTm as LA cations and (D) the formation of MQW structure with near-perfect Type I band alignment. 27 (E) PL spectra of BTm 2 SnI 4 and BTm 2 PbI 4 are compared to demonstrate the efficient energy transfer in the former system.…”

“…PeLEDs based on quasi-2D OSiPs. (A) Schematic diagram for “ n ” phase and molecular structures of four organic LA cations in quasi-2D perovskite with increasing bulkiness from left to right; their capability to control n phase distribution and suppress high n phase perovskites after thermal annealing is characterized by absorption spectra and shown in panel B . (C) A scheme of 2D perovskite lattice using BTm as LA cations and (D) the formation of MQW structure with near-perfect Type I band alignment .…”