Preparation Of Anti-reflection Coatings For Four-junction Ga As Solar Cell By Electron Beam Evaporation And Its Performance Research

GaAs-based ?-? solar cells have a wide range of applications in the space energy field due to their advantages such as high photoelectric conversion efficiency,good anti-irradiation performance,high temperature resistance,and strong reliability.Compared with the GaInP/GaAs/Ge triple-junction solar cell,the band matching of the GaInP/GaAs/InGaAs/InGaAs four-junction cell is more ideal.Furthermore,in order to improve the photoelectric conversion efficiency of the four-junction solar cell,in addition to optimizing the structure of the solar cell,it is also possible to increase the light utilization of the solar cell by designing an anti-reflection coating?ARC?.Therefore,based on the traditional TiO₂/Al₂O₃ double-layer ARC,a low-refractive-index MgF₂ material is used to form a TiO₂/Al₂O₃/MgF₂ triple-layer ARC system to achieve effective anti-reflection?AR?in a wider spectrum.Electron beam evaporation?EBE?technology completes the preparation.The main research contents are as follows:?1?By using the Macleod software,the TiO₂/Al₂O₃/MgF₂ triple-layer ARC was optimized and analyzed in the light band of 300nm-1800nm.The simulation results show that when the center wavelength is 450nm,the physical thickness of TiO₂,Al₂O₃ and MgF₂ films are 47.83nm,69.53nm and 69.53nm,the average reflectivity?Ra?of the coating is the lowest in the absorption band?880-1240 nm?of the current-limiting junction,which is 2.71%,and the Ra value of 8.11%in the 300nm to1800nm band.At this time,the AR performance of the film system based on the IMM-4J solar cell is the best,and the film system is more sensitive to the refractive index of Al₂O₃ film and the thickness of TiO₂ film,and is not sensitive to the incident angle of the sun less than 50°.?2?The average roughnesses of the amorphous TiO₂,Al₂O₃ and polycrystalline MgF₂ films prepared by the EBE technology were 0.48nm,0.44nm,and 1.20nm,respectively.The surfaces of the films were neat and dense.The effects of oxygen partial pressure,electron beam current,and substrate temperature on the refractive index and dispersive power of each single-layer film were investigated by comparative experiments.Among them,the substrate temperature has a greater impact on the refractive index and dispersive power of the films.The refractive index and dispersive power of TiO₂,Al₂O₃,and MgF₂ films increase with increasing electron beam current and substrate temperature;the refractive index and dispersive power of TiO₂ film decrease with increasing oxygen partial pressure.The performance of TiO₂ film is more affected by process parameters.?3?There are no obvious holes between the layers of the TiO₂/Al₂O₃/MgF₂triple-layer ARC prepared on the GaAs substrate,and the bonding is firm and the optical performance is good.The measured and simulated reflection curve changes in the same way.The Ra in the 300-1800nm band is 9.68%,which is close to 8.11%of the simulated value;the value in the 880-1240nm band is 3.30%,which is slightly higher than the 2.71%simulated value;the slight error is mainly due to the lack of TiO₂ film thickness.?4?Apsys software simulation results show that compared with a four-junction GaAs solar cell without an ARC,a TiO₂/Al₂O₃/MgF₂ triple-layer ARC with a center wavelength of 450 nm can greatly increase the short-circuit current density of third-junction and multi-junction solar cell,and their values have increased from11.69 and 11.69 to 16.49 and 16.50 mA/cm²,respectively.The ARC system promotes the current matching among the sub-junctions and improves photoelectric conversion efficiency of the multi-junction solar cell.