Transport layer engineering towards lower threshold for perovskite lasers.

Charge transport layers are essential for achieving electrically pumped perovskite lasers. However, their role in perovskite lasing is not fully understood. Here, we explore the role of charge transport layers on the lasing actions of perovskite films by investigating the amplified spontaneous emission (ASE) thresholds. We demonstrate a largely reduced ASE threshold and enhanced ASE intensity by introducing an additional hole transport layer poly(triaryl amine) (PTAA). We show that the key role of the PTAA layer is to accelerate the hot carrier cooling process by extracting holes in perovskites. With reduced hot holes, the Auger recombination loss is largely suppressed, resulting in decreased ASE threshold. Our argument is further supported by the fact that the ASE threshold can be further reduced from 25.7 to 7.2 μJ/cm upon switching the pumping wavelength from 400 nm to 500 nm to directly avoid excess hot hole generation. Our work for the first time exemplifies how to further reduce the ASE threshold with transport layer engineering through hot hole manipulation. This is critical to maintaining the excellent gain properties of perovskites when integrating them into electrical devices, paving the way for electrically pumped perovskite lasers. This article is protected by copyright. All rights reserved.