Proceedings of Online nanoGe Fall Meeting 20 (OnlineNFM20)
Publication date: 4th October 2020
Abstract
Organic-inorganic halide perovskites are promising as the light absorber of solar cells because of their efficient solar power conversion. Power conversion efficiencies (PCEs) of perovskite solar cells (PSCs) have already reached a very high level of up to 25.2 %, which is comparable to silicon solar cell technology. Most of high-performing PSCs reported to date contain a small molecular hole transport layer (HTL) material of 2,2',7,7'-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9'-spirobifluorene (spiro-OMeTAD). An issue frequently occurring in spiro-OMeTAD-based PSCs is quick performance degradation at high temperature. In this study, we discover that post-doping of the spiro-OMeTAD layer by iodine released from the perovskite layer is one possible mechanism of the high-temperature PSC degradation. The iodine doping leads to the highest occupied molecular orbital level of the spiro-OMeTAD layer becoming deeper and, therefore, induces the formation of an energy barrier for hole extraction from the perovskite layer. We demonstrate that it is possible to suppress the high-temperature degradation by employing an iodine-blocking layer or an iodine-free perovskite in PSCs. These findings will guide the way for the realization of thermally stable perovskite optoelectronic devices in the future.