Zhou Qiaohui, Zhou Hongzhi, Tao Weijian, Zheng Yizhen, Chen Yuzhong, Zhu Haiming
State Key Laboratory of Modern Optical Instrumentation, Centre for Chemistry of High-Performance and Novel Materials, Department of Chemistry, Zhejiang University, Hangzhou 310027, Zhejiang China.
Nano Lett. 2020 Nov 11;20(11):8212-8219. doi: 10.1021/acs.nanolett.0c03328. Epub 2020 Oct 12.
Multiple exciton generation (MEG) in semiconductors that yields two or more excitons by absorbing one high-energy photon has been proposed to break the Shockley-Queisser limit and boost photon-to-electron conversion efficiency. However, MEG performance in conventional bulk semiconductors or later colloidal nanocrystals is far from satisfactory. Here, we report efficient MEG in few-layer black phosphorus (BP), a direct narrow bandgap two-dimensional (2D) semiconductor with layer-tunable properties. MEG performance improves with decreasing layer number and reaches 2.09 threshold and 93% efficiency for two-layer BP, approaching energy conservation limit. The enhanced MEG can be attributed to strong Coulomb interaction and high density of states in 2D materials. Furthermore, MEG of BP shows negligible degradation in vertical heterostructure and multielectron can be extracted by interfacial transfer with near unity yield. These results suggest 2D semiconductors as an ideal system for next generation highly efficient light emission and charge transfer devices.
半导体中的多激子产生（MEG）通过吸收一个高能光子产生两个或更多激子，这被认为可以突破肖克利-奎塞尔极限并提高光子到电子的转换效率。然而，传统体半导体或后来的胶体纳米晶体中的MEG性能远不能令人满意。在此，我们报道了在少层黑磷（BP）中的高效MEG，BP是一种具有层可调特性的直接窄带隙二维（2D）半导体。MEG性能随着层数的减少而提高，对于两层BP，达到了2.09的阈值和93%的效率，接近能量守恒极限。增强的MEG可归因于二维材料中强烈的库仑相互作用和高态密度。此外，BP的MEG在垂直异质结构中显示出可忽略不计的降解，并且多电子可以通过界面转移以接近单位产率提取。这些结果表明二维半导体是下一代高效发光和电荷转移器件的理想系统。
