Tailoring carrier dynamics by band alignment engineering in quasi-2D perovskite LED

Band alignment of semiconductors is a crucial factor in constructing efficient optoelectronic devices. However, no studies have reported on the impact of phase distribution in quasi-2D lead halide perovskites on band alignment and carrier dynamics. Herein, an alteration in band alignment is achieved by intentionally optimizing phase distribution in a (PEA)₂CsPb₂I₇ quasi-2D film via the addition of a crown ether. It is experimentally evidenced that the band alignment can be engineered from type II to type I for the crown-induced narrowing of phase distribution, which results in enhanced electron-phonon coupling and increased exciton binding energy. As a consequence, accelerated hot carrier cooling, suppressed Auger recombination, and enhanced exciton recombination are observed in the crown-treated sample. Finally, benefited from band alignment engineering, the peak external quantum efficiency of the constructed light-emitting diode is improved from 7.4% to 20.1%.

https://pubs.acs.org/doi/abs/10.1021/acs.nanolett.5c04309