Organic Self-Assembled Monolayers as Hole Transport Layer in Inverted Perovskite Solar Cells

Perovskite solar cells (PSCs) are considered as one of the most promising new generation solar cells with a low-cost manufacturing process and impressive power conversion efficiency (PCE). In particular, inverted PSCs show good prospects for commercialization due to their relatively mild preparation conditions, simple process, and easy preparation into flexible large-area devices. In recent years, self-assembled monolayers (SAMs) have been widely applied as superior hole transport layers (HTLs) for state-of-the-art inverted PSCs to enhance the device performance. This review introduces the recent studies on SAM-based hole transport layers (SAM-HTLs), summarize and comment on their properties, and discuss the relationship between molecular structure and performance parameters of devices. The classification and analysis are conducted according to both the types of anchoring groups and the number of anchoring groups in SAMs. Finally, based on the current research, the future design of new efficient SAMs is prospected.