Carrier funnel switch in quasi-two-dimensional perovskites

Quasi-two-dimensional (quasi-2D) perovskites have attracted considerable attention and have been applied to a variety of novel optoelectronic devices due to their specific layered structure and carrier migration properties. Effectively controlling the carrier motion in perovskites with different phases is a crucial factor affecting their optoelectronic performance. Through Cs ions doping, single crystal PEA₂PbI₄ (PEA: phenethylamine) perovskites with n = 1 and n = 2 (n is an integer, representing the number of highly conductive [PbI]⁴⁻ layers) dule phases have been successfully prepared. It is found that temperature can be used as a switch for the carrier funnel effect of the two phases. At low temperatures, the carrier funnel is open and the carrier is effectively and directionally driven to the n = 2 phase due to the type I bandgap alignment of the heterostructure. As the temperature increases, the bandgap alignment of the heterostructure is carried over to type II, where the carrier channel is closed. Time-resolved photoluminescence (TRPL) spectra show that the highest energy input efficiency is achieved at 80 K. The study provides a feasible strategy for improving the energy transfer efficiency in mixed-phase perovskites.