Rubidium Iodide-Doped Spiro-OMeTAD as a Hole-Transporting Material for Efficient Perovskite Photodetectors

2,2',7,7'-Tetrakis-(N,N-di-p-methoxyphenylamine)-9,9'-spirobifluorene (spiro-OMeTAD) is one of the broadly used hole transport materials for high-performance perovskite photodetectors. However, to achieve high hole mobility and conductivity, it often requires the addition of additives and dopants with hygroscopic properties similar to bis-(trifluoromethane)sulfonamide lithium salt (Li-TFSI) and 4-tertbutylpyridine (TBP), which are forced to undergo aggregation and hydrolysis under environmental conditions, hence leading to pinholes/voids in resultant films. In this work, we added rubidium iodide (RbI) to spiro-OMeTAD together with Li-TFSI and TBP, and the complexation between RbI and TBP prevented the evaporation of TBP that hinders the aggregation of Li-TFSI and reduces the undesired voids. Consequently, RbI-doped spiro-OMeTAD serves as the hole transport layer (HTL) for perovskite photodetectors, enhancing the conductivity and hole transport abilities of the hole transport layer, which also helps to promote energy-level matching with the perovskite layer. The performance of the perovskite photodetector is verified by analyzing the current density-voltage characteristics as well as the transient and dynamic photocurrent response characteristics. Devices with RbI-doped HTLs exhibit a champion specific detectivity approaching 3.77 X 10(13) Jones and a linear dynamic range of 114 dB. This work provides a feasible approach to improve the stability of small-molecule-based hole transport materials for perovskite photodetectors.