Department of Chemistry and Centre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore , 3 Science Drive 3, Singapore 117543, Singapore.
National Engineering Research Center of Electromagnetic Radiation Control Materials and State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China , Chengdu 610054, China.
ACS Nano. 2016 Jun 28;10(6):6383-91. doi: 10.1021/acsnano.6b02845. Epub 2016 Jun 3.
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., MoS2) and a strongly absorbing material with long electron-hole diffusion lengths such as methylammonium lead halide perovskites (CH3NH3PbI3) 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 CH3NH3PbI3/MoS2 interface can be overcome by creating sulfur vacancies in MoS2 using a mild plasma treatment; ultrafast hole transfer from CH3NH3PbI3 to MoS2 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.
光伏器件的性能强烈依赖于吸收层的光捕获特性以及施主/受主界面处的电荷分离。原子层厚的二维过渡金属二卤化物（2-D TMDCs）表现出强烈的光物质相互作用、大的光学电导率和高的电子迁移率；因此，它们可能是下一代超薄太阳能电池和光电子学的极有前途的材料。然而，这种原子层厚的固有短光吸收路径限制了其实际应用。一种包含二维 TMDC（例如 MoS2）和具有长电子-空穴扩散长度的强吸收材料（例如甲基铵铅卤化物钙钛矿（CH3NH3PbI3））的异质结构几何形状可能在一定程度上克服这一限制，前提是异质结构界面处的电荷转移不会受到它们的能带偏移的阻碍。在此，我们证明了通过使用温和的等离子体处理在 MoS2 中创建硫空位，可以克服 CH3NH3PbI3/MoS2 界面处的固有能带偏移；光激发后，CH3NH3PbI3 向 MoS2 中发生超快的空穴转移，在 320fs 内的效率为 83%。重要的是，我们的工作突出了应用缺陷工程二维 TMDC 作为钙钛矿基光电设备中的电荷提取层的可行性。
