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 MoSe2 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:20,30-d0)-s-indaceno[1,2-b:5,6-b0)dithiophene (ITIC), PM6:Y6, and PM6:L8-BO-based OSCs with MoSe2 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 MoSe2 QDs HTLs due to suppressed interfacial chemical reactions. These results indicate that ultrathin MoSe2 QDs are a promising candidate material for HTL, providing a novel approach to further improving the performance of OSCs.