高效GaInP/GaAs双结叠层太阳能电池中载流子产生、复合和输运等细致光物理过程的综合研究

在本项研究中，我们提出以先进的综合性光学技术深入研究GaInP/GaAs双结叠层太阳能电池内部的基本光电子过程如光子吸收、光生载流子复合与输运过程，为实现超级高效叠层太阳电池提供生长和设计上的指引。我们拟采用宽范围波长可调的激光系统结合共聚焦显微以及时间分辨技术，实现具有准确纵向空间分辨能力的光学激发和探测，以期实现对半导体复杂叠层结构的光电子的选择性激发和表征。我们将利用该项功能强大的技术研究和测量少数载流子寿命、再复合速度、扩散长度等动力学参数，为高效广谱半导体太阳能电池的设计和制备提供可靠的基础数据。我们将通过本项技术的研发和应用，以及发表高水平的研究论文，为我国在高效率宽广谱多结叠层太阳能电池的基础研究上获得重要的知识突破做出杰出贡献。此外，通过本项目的实施，将为我国在先端的高效太阳能电池领域培养多名青年科研人员。

Super-high-efficiency monolithic III-V compound tandem solar cells have attracted intense research and development attention over recently years because of the high energy conversion efficiency and promising potential for space and terrestrial concentrator applications. To achieve higher conversion efficiency, lots of efforts have been devoted to the improvement of cell structure designs and fabrication conditions. Besides optimizing the fabricating techniques, understanding the essential physics of light absorption and dynamical behaviors of photogenerated carriers in the III-V tandem solar cells is fundamentally important for the goal of realizing super high efficiency. Definitely, optical methods are the most direct and powerful tools to access the involved fundamental physics. However, despite numerous electrical characterization means, optical methods have been scarcely applied to the measurements of the III-V tandem solar cell system. In this project, we propose to develop a comprehensive and powerful optical technique to investigate the monolithic GaInP/GaAs tandem cells, focusing on the issues towards improving light absorption efficiency and charge collection efficiency. Profiting from a very powerful femtosecond laser system with an excellent tunable flexibility in both wavelength and intensity and the technique of confocal microscopy, we plan to develop a unique technique being capable of selective excitation of layered semiconductor structures in tandem cells by accurately controlling the penetration depth of excitation laser via accurately adjusting excitation wavelength and intensity. A variety of spectroscopic measurement methods will be combined with the proposed technique to enhance its characterization ability. Based on this powerful technical platform, both one-photon and two-photon induced photoluminescence (PL) measurements will be performed mainly in the GaInP layers to investigate the light excitation and emission mechanisms. Time-resolved PL and photocurrent measurements will be comparatively used to investigate the minority-carrier lifetimes in the GaInP/GaAs tandem cells. The minority-carrier lifetime, recombination velocity and carrier diffusion length will be investigated and determined. The implementation of comprehensive optical technique and the conduction of research activities with it not only reinforce the national standing in the cutting-edge technique of super-high-efficiency solar cells in the world, but also help training young talents in the field for the country.