Synergistic Effect of Defects Passivation and Energy Level Alignment Realizing P3HT-Based High-Efficiency CsPbI₃...

Poly (3-hexylthiophene) (P3HT) is one of the most efficient hole transport layers (HTLs) in perovskite solar cells (PSCs). However, surface and boundary defects in CsPbI₃, and energy level mismatch between CsPbI₃ and P3HT lead to a low power conversion efficiency (PCE) in P3HT-based CsPbI₃ PSCs. Here, a synergistic strategy with anti-solvent (sec-pentyl alcohol, 2-PA) and passivators (LiX, X = F, Cl, Br, I) is developed to promote the photovoltaic performance of P3HT-based CsPbI₃ PSCs. It is proved that the 2-PA washes away the residual DMF and DMAPbI₃, and assists the secondary growth of CsPbI₃ crystal. LiX not only can passivate iodine (I) vacancies, but also can reduce energy offset at CsPbI₃/P3HT interface, accelerating hole extraction process. Finally, an impressive efficiency of 19.26% is obtained due to the synergistic effect of defects passivation and energy alignment, which is 34.4% higher than the 14.32% achieved in Control cell. These findings prove that synergistic strategy of defects passivation and energy alignment is an effective way for realizing high-efficiency in P3HT-based CsPbI₃ PSCs.