Solution‐Processable Two‐Dimensional MoSe2 Quantum Dots as a Hole Transport Layer for Highly Efficient and Stable Nonfullerene Organic Solar Cells

Hole transport materials are critical to carrier separation, hole extraction, and stability of organic solar cells (OSCs). Poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) has been popularly used as hole transport layers (HTLs) in high‐efficiency OSCs, while the device stability is relatively low due to interfacial chemical reactions between active layer and PEDOT:PSS. Herein, two‐dimensional MoSe 2 quantum dots (QDs) are employed as a subphoto sensitizer and pinhole‐free HTL to replace PEDOT:PSS in OSCs. The power conversion efficiencies of PBDB‐T: 3,9‐bis(2‐methylene(3‐(1,1‐dicyanomethylene) ‐indanone))‐5,5,11,11‐tetrakis(4‐hexylphenyl)dithieno‐[2,3‐d:2′,3′‐d′]‐s‐indaceno[1,2‐b:5,6‐b′]dithiophene (ITIC), PM6:Y6, and PM6:L8‐BO‐based OSCs with MoSe 2 QDs HTLs are 9.34%, 15.36%, and 18.29%, respectively, which are comparable to those (9.31%, 15.51%, and 18.22%) of the control devices with PEDOT:PSS HTLs. More importantly, superior device stability is achieved in the OSCs with MoSe 2 QDs HTLs due to suppressed interfacial chemical reactions. These results indicate that ultrathin MoSe 2 QDs are a promising candidate material for HTL, providing a novel approach to further improving the performance of OSCs.