Oriented Organization of Poly(3‐Hexylthiophene) for Efficient and Stable Antimony Sulfide Solar Cells

Poly(3‐hexylthiophene) (P3HT), as a traditional organic hole‐transporting material (HTM), is widely used in thin‐film solar cells due to its high charge mobility and good thermal stability. However, the P3HT films obtained by the traditional method are amorphous, which is unfavorable to hole extraction and transport. Here, a low‐toxicity solvent 1,2,4‐trimethylbenzene (TMB) was used as the solvent instead of the commonly used halogen solvent chlorobenzene (CB) to dissolve P3HT. Thus, the self‐assembled nanofibrous P3HT film was prepared and applied as HTM in the newly emerged Sb 2 S 3 solar cells. According to the density functional theory calculations, the interface contact between TMB‐P3HT and Sb 2 S 3 was enhanced via the bonding interaction of S in P3HT and Sb in Sb 2 S 3 . Through transient absorption spectroscopy characterization, the enhanced interface contact improves the charge extraction ability of TMB‐P3HT when compared to the CB‐P3HT film. Thus, the TMB‐P3HT‐based Sb 2 S 3 solar cell delivers a power conversion efficiency of 6.21%, which is 9.7% higher than that of the CB‐P3HT‐based device. Furthermore, the dopant‐free TMB‐P3HT‐based Sb 2 S 3 devices exhibit excellent environmental stability compared with Spiro‐OMeTAD‐based devices. This work demonstrates that the application of P3HT and the solvent engineering of HTM are applicable strategies for developing Sb 2 S 3 solar cells with high efficiency and stability.