LiTFSI-Free Hole Transport Materials for Robust Perovskite Solar Cells and Modules with High Efficiencies

Abstract

Lithium bis(trifluoromethane) sulfonamide (LiTFSI) and oxygen-doped organic semiconductors have been frequently used to achieve record power conversion efficiencies of perovskite solar cells (PSCs). However, this conventional doping process is timeconsuming and leads to poor device stability due to the incorporation of Li ions. Herein, aiming to accelerate the doping process and remove the Li ions, we report an alternative p-doping process by mixing a new small-molecule organic semiconductor, N 2 ,N 2 ,N 7 ,N 7 -tetrakis (4methoxyphenyl)-9-(4-(octyloxy) phenyl)-9H carbazole-2,7-diamine (labeled OH44) and its preoxidized form OH44 + (TFSI − ). With this method, a champion efficiency of 21.8% has been achieved for smallarea PSCs, which is superior to the state-of-the-art EH44 and comparable with LiTFSI and oxygen-doped spiro-OMeTAD. Moreover, the stability of OH44-based PSCs is improved compared with those of EH44, maintaining more than 85% of its initial efficiency after aging in an ambient condition without encapsulation for 1000 h. In addition, we achieved efficiencies of 14.7 and 12.6% for the solar modules measured with a metal mask of 12.0 and 48.0 cm 2 , respectively, which demonstrated the scalability of this method.