Hydrophobic Cu(2)O Quantum Dots Enabled by Surfactant Modification as Top Hole‐Transport Materials for Efficient Perovskite Solar Cells

The utilization of an inorganic hole‐transport layer (HTL) is one of the most effective methods to improve the stability and reduce the cost of perovskite solar cells (PSCs). However, achieving high‐quality inorganic HTL films, especially HTL films in n‐i‐p structures, via solution processes remains a big challenge. Here, a simple surface modification strategy for low‐cost and stable cuprous oxide (Cu(2)O) quantum dots is proposed, which utilizes a silane coupling agent. The modified Cu(2)O can be directly deposited on the perovskite film as the top HTL without decomposing the perovskite to maintain an n‐i‐p structure. The efficiency (18.9%) of PSCs with surface‐modified Cu(2)O as the HTL is significantly higher than that (11.9%) of PSCs with unmodified Cu(2)O, which is also the record efficiency for a Cu(2)O‐based perovskite solar cell in n‐i‐p structure. The enhanced performance of PSCs is attributed to the remarkably enhanced film properties achieved through surface modification. Moreover, because of the dopant‐free technology and hydrophobic surface, the Cu(2)O‐based PSCs have distinctly better stability than 2,2′,7,7′‐tetrakis[N,N‐di(4‐methoxyphenyl)amino]‐9,9′‐spiro‐bifluorene‐based PSCs.