Experimental Verification of Thermal Damage Mechanism in Single Junction GaAs Solar Cells Irradiated by Laser

Three types of laser irradiating experiments on single junction GaAs solar cells were carried out. Different laser sources with the same energy coupling intensity, in-band (808 nm), out-of-band (1.07 mu m), or the combination of these two, are used to irradiate the solar cells. Based on the changes of current-voltage characteristic curves of irradiated solar cells, the damage degrees could be classified into three stages: gently, seriously and thoroughly damaged stages. The damage mechanism is studied from two aspects: 1) output changes of solar cell equivalent circuit under different configuration settings, 2) thermal analysis model. The results show that the damage degrees of gently and thoroughly damaged stages are similar in terms of insensitivity to irradiation intensity. However, they are different from seriously damaged stage, which is sensitive to irradiation intensity due to thermal decomposition of GaAs. Specifically, the composition causes the increase of PN junction defects, which leads to performance degradation of irradiated solar cells. In conclusion, the main reason for performance degradation of solar cells is the thermally initiated the increase of PN junction defects.