posted on 2022-02-03, 14:05authored byJunsheng Luo, Jinqing Zhu, Fangyan Lin, Jianxing Xia, Hua Yang, JinyuYang, Ruilin Wang, Junyu Yuan, Zhongquan Wan, Ning Li, Christoph J. Brabec, Chunyang Jia
The
bis(trifluoromethane)sulfonimide lithium salt (Li-TFSI) is
commonly used as an effective dopant to improve the conductivity and
hole mobility of Spiro-OMeTAD in state-of-the-art n–i–p
perovskite solar cells (PSCs). However, such doping severely induces
device instability because of the ultrahygroscopic and migratory nature
of Li+ ions. Here, we demonstrate a fluorinated Fe(F20TPP)Cl
with a hydrophobic property and a high migration barrier as a potential
alternative to replace the Li-TFSI in doped Spiro-OMeTAD. The optimized
PSCs show a champion power conversion efficiency as high as 21.53%
with a stabilized efficiency exceeding 21%. In addition, long-term
stability of PSCs is significantly improved, and the device retains
84% of its initial efficiency after 900 h under continuous 100 mW
cm–2 white light-emitting diode illumination and
89% of its initial efficiency after even 50 days in an ambient environment
without encapsulation. We believe that this work addresses the fundamental
question of intrinsic and extrinsic instability in Li-TFSI-based PSCs
by combining simulation and experimental studies. The novel dopant
Fe(F20TPP)Cl developed for Spiro-OMeTAD in this work can effectively
meet the demands of future photovoltaic applications with promising
efficiency and device stability.