Behavior of radiation-induced defects in GaInAsP solar cells under heat light soaking

To evaluate the compatibility of 1.5 eV Ga0.9In0.1As0.85P0.15 solar cells with the space environment, we investigated their radiation degradation characteristics and examined the behavior of the resulting defects under heat light soaking (HLS). The open-circuit voltage (Voc) of Ga0.9In0.1As0.85P0.15 solar cells was initially higher than that of GaAs solar cells; however, this relationship reversed following irradiation with 1 MeV electrons at a fluence of 3 × 1014 cm−2. On the other hand, only the Voc of Ga0.9In0.1As0.85P0.15 solar cells recovered after HLS and eventually surpassed that of GaAs solar cells. Light soaking improved the defect recovery rate and reduced the activation energy of defect recovery in Ga0.9In0.1As0.85P0.15 solar cells, suggesting that light soaking accelerates the defect recovery phenomenon that occurs under dark conditions. Furthermore, by performing HLS while varying the operating point of the solar cell, we clarified that the extent of recovery is determined by the density of recombination carriers in the solar cell. We discuss the overall radiation resistance of Ga0.9In0.1As0.85P0.15 solar cells, including their recovery phenomenon in the orbital environment.