Degradation analysis of 3J InGaP/InGaAs/InGaAsN solar cell due to irradiation induced defects with a comparative study on bottom homo and hetero InGaAsN subcell

The influence of irradiation induced traps in the triple junction In0.49Ga0.51P/In0.01Ga0.99As/In0.30Ga0.70As0.98N0.02 solar cell was studied using finite element analysis. The total 3J solar cell structure was simulated separately with homo and hetero InGaAsN structure as the third or bottom subcell. The higher efficient 3J InGaP/InGaAs/InGaAsN solar cell with bottom InGaAsN heterostructure was analyzed by including irradiation induced trap levels. The trap levels correspond to 1 MeV electron irradiation with fluence range of 1 × 1014-1 × 1016 in electrons/cm2 at room temperature. We realized that the traps in the middle cell cause more degradation, followed by bottom cell and then top cell. The onset of degradation of solar cell parameters (Jsc, Voc and η) starts at trap concentration 1 × 1013 cm−3, while more degradation occurs beyond 1 × 1016 cm−3. At trap concentration of 1 × 1016 cm−3, the solar cell design was optimized for achieving current matching among the subcells. While we obtained 36% conversion efficiency at 1-sun (AM0 spectrum) using bottom heterostructure, the introduction of 1 × 1016 cm−3 trap concentration and 104 cm/s surface recombination velocity simultaneously in all subcells resulted in 20.8% conversion efficiency which increased to 24.3% after current matching.