Multiple Roles of Cobalt Pyrazol-Pyridine Complexes in High Performing Perovskite Solar Cells.

Abstract

Chemical doping is a ubiquitously applied strategy to improve the charge-transfer and conductivity characteristics of spiro-OMeTAD, a hole-transporting material (HTM) used widely in solution-processed perovskite solar cells (PSCs). Cobalt(III) complexes are among the commonly employed HTM dopants, which major role is to oxidize spiro-OMeTAD, i.e. provide p-doping for better conductivity. The present work discloses additional, previously unknown important functions of cobalt complexes in the HTM films that influence the photovoltaic performance. Specifically, it is demonstrated that commercial p-dopant FK269 (bis(2,6-di(1H-pyrazol-1-yl)pyridine) cobalt(III) tris(bis(trifluoromethylsulfonyl)imide)) reduces the interfacial recombination and alleviates the decomposition and corrosion of perovskite active material under the action of tert-butylpyridine and lithium bis(trifluoromethanesulfonyl)imide. These effects are demonstrated for 1-cm2 sized PSCs that achieve a stabilized PCE of 19 % under 1 sun irradiation.