III-V多结太阳电池目前光电转换效率最高，是当前空间飞行器的主电源，同时辅以廉价聚光系统可以在大规模工业发电系统中广泛应用，被称为第三代太阳电池。当前广为使用的GaInP（1.9eV）/GaAs（1.4eV）/Ge（0.67eV）结构尽管晶格匹配，但顶/底电池吸收范围不够宽，与太阳光谱不匹配，表现为GaInP顶电池和Ge底电池电流偏大，使电池效率限制在31～32%。改进之一是在1.4eV以上引入1.7eV与2.05eV材料，而这些带隙所对应的半导体材料和目前不同，能带排列和器件结构也相差很大，尤其是连接它们的2.0-2.1eV宽带隙异质隧穿结。本项目中，综合运用能带工程和材料调控两种方法，从理论和实验上开展针对宽带隙1.7-2.05eV异质结太阳电池及2.0-2.1eV宽带隙异质隧穿结物理特性与制备方法研究，在此基础上结合先期具备的窄带隙双结及材料集成技术，制备高效5结太阳电池。

The multijunction solar cell based on III-V semiconductors now has the highest conversion efficiency benefited from the excellent material quality and carrier transport mechanism。 It serves as the main solar energy collector on space vehicles, and also can be apllied to grid electrity generation with cheap optical concentration system, i.e. the so-called third generation solar cell. The state-of-art GaInP(1.9eV)/GaAs(1.4eV)/Ge(0.67eV) triple-junction solar cell, despite the lattice match, has a upper limit (31-32 percent) of the conversion efficiency due to the mismatch between the bandgap distribution and the solar spectra. The practical results show that the GaInP subcell and the Ge subcell have excess photo-current resulted from their narrow bandgaps. One key improvement is to introduce 1.7eV and 2.05eV wide bandgap materials to ultilize the short wavelength light more efficiently than the current structure. However, the material properties corresponding to these bandgaps are different from thoses currently used, leading to the great changes of the energy band lineups and the device structures . Moreover, the tunneling diode connecting these wide bandgap subcells should increase its bandgap to nearly 2.0-2.1eV. In this project, by engineering the energy band and the material property, we are going to conduct the researches of the heterostructure solar cells with 1.7eV and 2.05eV materials, and together with the 2.0-2.1eV tunneling diodes. Finally, based on mature narrow band-gap materials and integration technology, we hope to achieve a high-efficiency five-junction solar cell.