P3HT with Zn(C6F5)(2) as p-Type Dopant for the Enhanced Performance of Planar Perovskite Solar Cells

The molecular organic Lewis acid bis(pentafluorophenyl)zinc [Zn(C6F5)(2)] is reported as an efficient p-type dopant for poly(3-hexylthiophene-2,5-diyl) (P3HT), to be used as hole-transporting material (HTM) in perovskite solar cells (PSCs) for the first time. To date, the most efficient PSCs use lithium bis(trifluoromethane)sulfonimide lithium salt (LiTFSI) and 4-tert-butylpyridine (tBP) as standard additives for HTMs. However, such dopants can induce deleterious effects on device stability. Herein, the effect of the concentration of Zn(C6F5)(2) in P3HT HTM on the performance of PSCs is investigated. The P3HT-based PSCs using a low concentration of the dopant (0.025 mol%) in the HTM layer exhibit the best performance and the highest power conversion efficiency (PCE) of 17.49%, which is almost 3.5% higher than the achieved PCE for pristine P3HT-based PSCs. The origin of the improved performance for PSCs is further investigated, by studying the conductivity and hole mobility of the thin films based on pristine and doped P3HT. Adding a small amount of Zn(C6F5)(2) to P3HT increases its thin-film hole mobility and its hole extraction ability.