2, University of Kentucky, Lexington, Kentucky, United States
3, University of Kentucky, Lexington, Kentucky, United States
Organometal halide perovskite (OHP) photovoltaic (PV) cells have shown dramatic increases in power conversion efficiency over the previous 7 years, yet they still face a number of challenges that must be met to enable widespread commercialization. Meeting these challenges involves material and interface development and optimization throughout the whole photovoltaic device stack. OHP photovoltaics usually contain both electron and hole transport layer (HTL), which influence charge extraction, recombination, and thus the overall PV performance. Herein, we introduce a new family of triarylaminoethynyl silanes moieties as HTLs to investigate how the photovoltaic performance depends on the ionization energy (IE) of the HTL and provide a new and versatile HTL material platform. We find that all molecules in this series of triarylaminoethynyl silanes can serve as efficient HTLs for OHP PVs, despite the 0.5 eV variation in IEs. We further studied the influence of the HTL IE on the PV performance of Methylammonium lead iodide (MAPbI3) based devices, by applying a series of eleven different hole transport materials with IEs varying from 4.74 to 5.84 eV. The ideal HTL IE range for maximum PV efficiency is dependent on the perovskite processing conditions. In the Pb(OAc)2 processed devices, 4.8 to 5.3 eV is found to yield the maximum PV performance, while in the PbI2 processed devices the performance is relatively insensitive to HTL IE between 4.8 and 5.8 eV.