Highly efficient and stable perovskite solar cells using thionyl chloride as a p-type dopant for spiro-OMeTAD

Hole transport materials (HTMs) play an important role in perovskite solar cells (PSCs). At present, the most frequent used HTM is spiro-OMeTAD. However, spiro-OMeTAD without dopants have low electrical conductivity and hole mobility. Therefore, the improvement of mobility and conductivity of hole transport layer (HTL) has become a crucial issue. Here, we introduce a dopant, thionyl chloride (SOCl2), to oxidize spiro-OMeTAD and generate more spiro-OMeTAD(+). Under the same conditions, the optimized device doped with SOCl2 achieves a power conversion efficiency (PCE) of 20.76%, while the pristine one is only 18.13%. The doping of SOCl2 not only reduces the density of defect states at the interface between perovskite and HTL, but also suppresses the recombination of light-induced carriers. In addition, the stability of the PSCs based on SOCl2 is greatly improved, which can maintain 90% of the initial PCE for 31 days under ambient conditions. This work provides a simple and feasible strategy for dopant engineering of HTL to achieve efficient PSCs. (C) 2020 Elsevier B.V. All rights reserved.