Investigation of Chemical Origin of White-Light Emission in Two-Dimensional (C4H9NH3)2PbBr4 via Infrared Nanoscopy.

The broadband light emission in low-dimensional organic lead halide perovskites (OHPs) is a fascinating property for white light-emitting diodes (LEDs). However, unique emission has been observed in highly distorted low-dimensional OHPs such as (110) and (111) perovskites. Herein, we report the first observation of white-light emission under ambient (21 °C) conditions in a rectangular microsheet of (C4H9NH3)2PbBr4, a (100) perovskite. The origin of white-light emission in (C4H9NH3)2PbBr4 was revealed as defect-assisted radiative recombination via excitation power-dependent photoluminescence measurement. Additionally, the origin of the defect was confirmed to be organic cation vacancies formed by intercalated water molecules via infrared nanoscopy. This result can help to improve the performance of white LEDs using low-dimensional OHPs.