Doping organic hole-transport materials for high-performance perovskite solar cells

Single-junction and tandem perovskite solar cells(PSCs)have achieved impressive power conversion efficiencies(PCEs)of 25.7%and 31.3%,respectively,which makes it to be one of next-generation photovoltaic technologies[1−9].Inter-face engineering[3,5,10−12],composition engineering[13]and ad-ditive engineering[7,14,15]have made remarkable contribu-tions to efficiency enhancement.Compared with efficiency,the long-term operational stability of PSCs jogs along,which is far from the requirements of commercialization.Currently,almost all regular n-i-p PSCs were accomplished with classic-al organic hole-transport materials(HTMs),i.e.,PTAA[16]and spiro-OMeTAD[2,4,6].However,the highly efficient PSCs with the above organic hole-transport layers(HTL)usually suffer from instability.To facilitate hole transport and extraction,LiTF-SI and tBP are frequently employed to dope organic HTLs but this would sacrifice device stability.The use of these hygro-scopic p-dopants endows the devices with poor moisture sta-bility.