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 transportlayers(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 toimproved charge transport properties in the PTAA and can also enhancecharge transport, leading to improved device efficiency of the resultingperovskite solar cell. 343FP reduces the highest occupied molecularorbital energy level of PTAA, improves the conductivity of HTLs, andpassivates the interface defects, and the optimized device of 343FPshows a champion efficiency of 20.02%. In addition, due to the hydrophobicityof 343FP, compared with the traditional hygroscopic dopant lithiumbis((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 anew method for the optimization of high-efficiency and high-stabilityperovskite photovoltaic hole transport layers.