MoS2 Quantum Dots with a Tunable Work Function for High-Performance Organic Solar Cells.

An efficient hole extraction layer (HEL) is critical to achieve high-performance organic solar cells (OSCs). In this study, we developed a pinhole-free and efficient HEL based on MoS2 quantum dots (QDs) combined with UV-ozone (UVO) treatment. The optophysical properties and morphology of MoS2 QDs and their photovoltaic performance are investigated. The results showed that MoS2 QDs can form homogeneous films and can be applied as an interfacial layer not only for donors with shallow highest occupied molecular orbital (HOMO) but also for those with deep HOMO energy levels after UVO treatment (O-MoS2 QDs). The solar cells based on O-MoS2 QDs yield a power conversion efficiency (PCE) of 8.66%, which is 71% and 12% higher than those of the OSCs with pristine MoS2 QD and O-MoS2 nanosheets, respectively, and the highest PCEs for OSCs containing MoS2 materials. Furthermore, the stability of solar cells based on MoS2 QDs is greatly improved in comparison with state-of-the-art PEDOT:PSS. These results demonstrate the great potential of O-MoS2 QDs as an efficient HEL for high-performance OSCs.