文摘
The performance of a photovoltaic device is strongly dependent on the light harvesting properties of the absorber layer as well as the charge separation at the donor/acceptor interfaces. Atomically thin two-dimensional transition metal dichalcogenides (2-D TMDCs) exhibit strong light–matter interaction, large optical conductivity, and high electron mobility; thus they can be highly promising materials for next-generation ultrathin solar cells and optoelectronics. However, the short optical absorption path inherent in such atomically thin layers limits practical applications. A heterostructure geometry comprising 2-D TMDCs (e.g., MoSb>2b>) and a strongly absorbing material with long electron–hole diffusion lengths such as methylammonium lead halide perovskites (CHb>3b>NHb>3b>PbIb>3b>) may overcome this constraint to some extent, provided the charge transfer at the heterostructure interface is not hampered by their band offsets. Herein, we demonstrate that the intrinsic band offset at the CHb>3b>NHb>3b>PbIb>3b>/MoSb>2b> interface can be overcome by creating sulfur vacancies in MoSb>2b> using a mild plasma treatment; ultrafast hole transfer from CHb>3b>NHb>3b>PbIb>3b> to MoSb>2b> occurs within 320 fs with 83% efficiency following photoexcitation. Importantly, our work highlights the feasibility of applying defect-engineered 2-D TMDCs as charge-extraction layers in perovskite-based optoelectronic devices.