Effects of Choline Chloride in Lead Bromide Layer and Methylammonium Bromide Precursor on Perovskite Conversion and Optoelectronic Properties of Perovskite-Based Light-Emitting Diodes

The effects of the addition of choline chloride (ChCl) during perovskite synthesis are investigated in this report. The addition of ChCl in the lead bromide (PbBr2) layer could improve the optoelectronic properties of perovskite due to the passivation of defects. Besides, the addition of ChCl in methylammonium bromide (MABr) precursor severely affected the conversion time and optoelectronic properties of perovskite. The conversion time of perovskite with a precursor of MABr and ChCl was 8 times shorter than that of perovskite with only the MABr precursor at the low reaction temperature of 60 °C. During perovskite conversion reaction, the addition of ChCl in the MABr precursor modified the morphology and shifted the absorption edge of perovskite to a short wavelength. Since the addition of ChCl in the PbBr2 layer and the addition of ChCl in the MABr precursor could passivate defects of perovskite, the optoelectronic properties of perovskite were improved, such as extending the decay time of time-resolved photoluminescence (TRPL). The TRPL decay time of perovskite was extended from 7.7 to 23.9 ns when appropriate ChCl was added in the PbBr2 layer and the MABr precursor. Consequently, compared with the perovskite-based light-emitting diodes (PeLEDs) converted by the PbBr2 layer and the MABr precursor without ChCl, PeLEDs converted by the appropriate ChCl in the PbBr2 layer and the MABr precursor presented more than 5 and 8 times enhancements in maximum brightness and maximum current efficiency, respectively.