Radiation Damage Effect And Simulation Of Space GaAs Solar Cells

Based on the electrical parameters of GaAs/Ge single-junction solar cells and GaInP/GaAs/Ge triple-junction solar cells irradiated by AM0 spectrum,this paper constructed physical models of the two cells using Silvaco TCAD to explore the influence mechanism of changing the thickness of working area and doping concentration on the performance parameters of solar cells.The equivalent electron ground irradiation experiment of GaAs/Ge single junction solar cell was carried out to explore the degradation law of electrical performance of solar cell under electron irradiation of 1Me V and 2Me V.Based on the experimental data of irradiation,silvaco TCAD was used to reproduce the state of the irradiated solar cell,determine the damage coefficient of minority carrier diffusion length and the removal rate of majority carriers after electron irradiation,and reveal the internal damage mechanism of GaAs/Ge single-junction solar cell.Firstly,the influence mechanism of structural parameters of GaAs/Ge single-junction solar cell on electrical performance is analyzed.The increase of the thickness of the transmitting region increases the utilization of the spectrum and the short-circuit current.However,when the thickness of the transmitting region is too large,the utilization of the spectrum in the base region will be affected and the short-circuit current will decrease.The open circuit voltage decreases as the short circuit current decreases.The increase of base thickness leads to the increase of short-circuit current first and then unchanged.The open circuit voltage is not affected by the thickness of the base region.The maximum power also varies with the short-circuit current.With the increase of the doping concentration in the working area,the scattering ability of minority carriers will be enhanced,which will shorten the diffusion length of minority carriers and reduce the short-circuit current.However,the increase of doping concentration will increase the solar cell’s built-in electric field,that is,the open circuit voltage.The maximum power also varies with the short-circuit current.Secondly,the influence mechanism of structural parameters of GaInP/GaAs/Ge triple junction solar cells is studied.The results show that the short-circuit current increases and then decreases with the thickness of GaInP top cell transmitting region,but decreases continuously with the thickness of base region.GaInP top cell is the reason of current limiting of three junction solar cell.The increase in the thickness of the working area leads to an increase in open circuit voltage.The maximum power varies with the short-circuit current.The short-circuit current decreases with the increase of GaAs cell working area thickness,and the open-circuit voltage increases slightly.However,GaAs cells limit the overall current when the emission and base region thicknesses increase.The change of doping concentration in GaInP roof battery has little effect on electrical parameters.The short-circuit current decreases with the increase of doping concentration in GaAs cell working area,but the open-circuit voltage increases slightly.The maximum power varies with the short-circuit current.When the doping concentration increases,GaAs cells are more affected by carrier scattering,which becomes the reason for current limiting of three-junction solar cells.Finally,the study on the irradiation effect of GaAs/Ge solar cells shows that when GaAs/Ge solar cells are irradiated by 1 Me V and 2 Me V electrons,the whole absorption band has a decline.With the increase of the injection amount,the decline becomes more serious.The degradation of short circuit current is greater than that of open circuit voltage.Moreover,the external quantum efficiency and electrical parameter decline of 2Me V electron irradiation are higher than that of 1 Me V electron.The damage mechanism of GaAs/Ge solar cells irradiated by 1Me V and 2Me V electrons was studied by silvaco TCAD.Irradiated by the same energy electron,the larger the electron flux,the shorter the lifetime of the minority electron,that is,the shorter the diffusion length of the minority electron.With the same amount of electron injection,the greater the electron energy is,the shorter the minority electron diffusion length is.Using the simulated minority diffusion length,the damage coefficients of the minority diffusion length in the emission region and the base region are 1.72×10^-7 and 2.76×10^-7,respectively,after 1Me V electron irradiation.After 2Me V electron irradiation,the damage coefficients of the scattering length in the emission region and the base region are 3.61×10^-7 and 5.63×10^-7,respectively.The larger the electron energy is,the larger the damage coefficient of the minority electron diffusion length is,and the more serious the damage of solar cell is.The attenuation of the minority cell diffusion length is the main reason for the decrease of short-circuit current of solar cells.Irradiated by the same energy electron,the larger the electron flux,the smaller the polyonic concentration,that is,the smaller the open circuit voltage.With the same amount of electron injection,the higher the electron energy is,the more obvious the polyonic concentration decreases.The polyonic concentration obtained by Silvaco TCAD simulation was fitted and calculated,and the removal rates of polyonic concentration in the base region after 1Me V and 2Me V electron irradiation were 221.2 cm^-1 and 240.1 cm^-1,respectively.The majority carrier removal effect is the main cause of open circuit voltage degradation.