Radiation resistance of GaAs solar cells and hot carriers

The role of hot carriers in enhancing the radiation resistance of GaAs solar cells has been investigated. The laser-pulse induced, short-circuit current response method was used to study solar cell degradation caused by radiation damage. Samples were subject to radiation doses in the range 1×1014–4×1016 electron cm−2 and then probed with laser pulses with 7 ns duration and 3.7 eV energy. We have developed a non-stationary theory of minority carrier flow in the active region of the solar cell. The theory allows a description of the temporal evolution of the short-circuit current and the dependence on irradiation dose. The model agrees well with experimental results using a single fitting parameter. This parameter is the carrier capture cross-section of radiation center E5 in the p-region emitter of the solar cell. The value of the cross-section was determined to be 0.1×10−12 cm2 from the results under non-stationary condition. This is seven times lower than that deduced from the current–voltage characteristics in the dark for a similar solar cell. The difference can be explained by a strong reduction of capture cross-section with increased carrier energy. Our results suggest that the observed cross-section reduction is caused by carrier accumulation at energies comparable with the optical phonon energy.

The GaAs solar cells short-circuit current response to laser pulse (1) decreases with doze of 1 Mev electron irradiation, lines 2–5. Photoexited hot carriers raise the radiation resistance of solar cells.Figure optionsDownload as PowerPoint slideHighlights
► The degradation of GaAs SCs irradiated 1 MeV electrons was studied with using pulsed laser source.
► The non-stationary theory of minority carrier flow in the active p-region of the SC was developed.
► The temporal evolution of short circuit current with irradiation dose is described by this theory.
► Carrier cross-section capture by radiation defect E5 is 7 times less compare to measured in dark.
► The difference is caused of reduction of capture cross-section for photoexited hot carriers.