Tri(4-trifluoromethylphenyl)phosphine-Modified Hole-Transport Material PTAA to Improve the Performance of Perovskite Solar Cells

The energy level alignment and conductivity of hole transport layers (HTLs) are critical to the performance of perovskite solar cells (PSCs). Additive engineering is an effective approach, and we introduced tri(4-trifluoromethylphenyl)phosphine (343FP) as an additive into poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA). Studies have shown that the addition of 343FP can lead to improved charge transport properties in the PTAA and can also enhance charge transport, leading to improved device efficiency of the resulting perovskite solar cell. 343FP reduces the highest occupied molecular orbital energy level of PTAA, improves the conductivity of HTLs, and passivates the interface defects, and the optimized device of 343FP shows a champion efficiency of 20.02%. In addition, due to the hydrophobicity of 343FP, compared with the traditional hygroscopic dopant lithium bis((trifluoromethyl)sulfonyl)azide (Li-TFSI)/4-tert-butylphenol (t-BP) bi-doped (Li-doped) PTAA and the undoped PTAA, the device with 343FP-doped PTAA has better environmental stability. After 1000 h of exposure to the environment, the efficiency of 78% of the original value can be maintained. This work will open up a new method for the optimization of high-efficiency and high-stability perovskite photovoltaic hole transport layers.