Abstract
The revision of InN bandgap to a much narrower value (≈0.7 eV) has opened the new research on InN-based solar cell. For InN-based materials, multi-junction solar cell seems to be the most promising approach, because a wanted bandgap between 0.6 and 2.5 eV can be obtained by using the alloy materials. Many groups have reported homojunction-type or sandwich-type InGaN solar cells. The maximum In content in InGaN absorption layers employed is around 0.3 (Eg≈2.3 eV). The low In content is the main reason for the poor performance of the present single-junction devices under the solar irradiance. To realize a high efficiency multi-junction cell, many issues, especially, the growth of high quality alloy films with an In content of 0.4-1 and the control of p-type doping, should be solved.
