Effects of proton irradiation on upright metamorphic GaInP/GaInAs/Ge triple junction solar cells

• Published in: Solar energy materials and solar cells 2018-10, Vol.185, p.36-44
• Main Authors: Aierken, A., Fang, L., Heini, M., Zhang, Q.M., Li, Z.H., Zhao, X.F., Sailai, M., Liu, H.T., Guo, Q., Gao, W., Gao, H., Sun, Q.
• Format: Article
• Language: English
• Subjects: Cathodoluminescence; Composition; Degradation; Diffusion length; Dislocation; Dislocation density; Energy efficiency; Gallium indium phosphide; Germanium; Indium; Indium gallium arsenides; Irradiation; Lattice matching; Metalorganic chemical vapor deposition; Minority carriers; Organic chemistry; Parameters; Photovoltaic cells; Proton beams; Proton irradiation; Protons; Quantum efficiency; Radiation; Radiation damage; Radiation tolerance; Reinforced reaction injection molding; Solar cell; Solar cells; SRIM; Strain analysis; Threading dislocations; Upright metamorphic; X-ray diffraction
• ISSN: 0927-0248; 1879-3398
• DOI: 10.1016/j.solmat.2018.04.035

The electrical parameters and external quantum efficiency (EQE) of 3 MeV and 8 MeV proton beam irradiated upright metamorphic (UMM) GaInP/GaInAs/Ge triple-junction solar cells, grown by metal-organic chemical vapor deposition, have been investigated and compared to lattice-matched (LM) GaInP/GaInAs/Ge solar cells. High-resolution X-ray diffraction was used to study the relaxation of strain by analysing reciprocal space maps. Threading dislocation density was estimated from cathodoluminescence image. SRIM simulation results have been applied for analysing the irradiation induced displacement damage and its effects on cell performance. The results show that the electrical parameters of both UMM and LM cells degraded more by 3 MeV proton compared to 8 MeV proton irradiation. The degradation of Voc and Isc depends on each other in both UMM and LM cells but have different features under proton irradiation due to different cell configurations, materials, and parameters etc. EQE spectra of UMM and LM cells mainly degrades in longer wavelength region due to the reduction of minority carrier diffusion length. Top GaInP subcell in UMM cell shows better radiation resistance than LM cell due to the higher In-P composition, and middle GaInAs middle subcell in UMM structure shows weaker radiation resistance because of the relatively higher indium composition. •MOCVD grown high quality upright metamorphic (UMM) GaInP/GaInAs/Ge triple-junction solar cells have been investigated upon 3 MeV and 8 MeV proton beam irradiation.•Degradation of electrical and spectral properties of UMM cells have been studied and compared to traditional lattice matched (LM) GaInP/GaInAs/Ge cell. Both UMM and LM cells degraded more by 3 MeV protons compared to 8 MeV proton irradiation.•A compositionally graded buffer layer has been applied to solve the lattice mismatch between middle and bottom subcells, strain relaxation reached 95%. Threading dislocation density in as-grown epilayer wafers controlled at 105 /cm2.•SRIM simulation results of irradiation have been applied for analysing the irradiation induced displacement damage and its effects on cell performance.•UMM configuration is a promising candidate for future space application considering relatively higher BOL and EOL efficiency compared to LM structure.