Radiation effects on strain compensated quantum dot solar cells

The effects of alpha-particle irradiation on the current-voltage characteristics and spectral responsivity of GaAs-based p-type / intrinsic / n-type solar cell devices containing 5-layers of InAs quantum dots (QD) grown with strain-compensation layers were investigated. The devices were subjected to ∼4.2 MeV alpha-particle irradiation and the variation in the air mass zero short circuit current, open circuit voltage, fill factor, efficiency, and spectral responsivity were monitored as function of fluence and displacement damage dose. The measured spectral responsivity values of the quantum dot solar cell at wavelengths above and below the GaAs bandgap were used to investigate the rate of degradation in the InAs QDs in comparison to that of bulk GaAs. A computational model was developed to study the effects of strain on the energy threshold for atomic displacement (knock-out energy) of indium and arsenic within an InAs QD. Using the many-body Tersoff potentials, the energy of the primary knock-on atom occupying various sites within the lattice was calculated as a function of strain. The observed increases in minimum knock-out energy and interstitial-site energy with strain suggest a potential mechanism for the increased radiation tolerance observed in Stranski-Krastanow grown QDs.