Less-Lead Control toward Highly Efficient Formamidinium-Based Perovskite Light-Emitting Diodes.

Area of Science:

• Materials Science
• Optoelectronics
• Nanotechnology

Background:

• Formamidinium (FA)-based perovskites are promising for efficient light-emitting diodes (LEDs) due to their favorable tolerance factors.
• Nonradiative recombination and device instability hinder the performance of current perovskite LEDs.

Purpose of the Study:

• To investigate the effect of stoichiometric modification, specifically reducing lead content, on the performance of FA-based perovskite nanocrystals for LEDs.
• To establish the influence of the lead (Pb) ratio on perovskite LED efficiency and operational stability.

Main Methods:

• Fabrication of FA cation-based perovskite nanocrystals FA_0.8Cs_0.2Pb_xBr₃ with varying lead ratios (x = 1.0, 0.8, 0.7, 0.6).
• Analysis of the impact of reduced lead precursor on inhibiting nonradiative recombination by minimizing uncoordinated metallic Pb atoms.
• Evaluation of device performance, including current efficiency and stability, under operating conditions.

Main Results:

• Reduced lead content effectively suppresses nonradiative recombination, leading to enhanced perovskite LED performance.
• The optimized composition FA_0.8Cs_0.2Pb_0.7Br₃ achieved a current efficiency of 28.61 cd A^-1, an 11-fold improvement over previous records.
• Stoichiometric optimization mitigated device degradation, attributed to reduced hydrogen reaction under moisture.

Conclusions:

• Stoichiometric optimization of lead in perovskite nanocrystals is a critical strategy for advancing perovskite LED technology.
• Less-lead perovskites offer a viable pathway to simultaneously improve efficiency and stability in optoelectronic devices.
• Further development of perovskite LEDs can be significantly aided by precise control over precursor stoichiometry.