Gamma Rays Induced Effects on the Performance of Silicon Solar Cells

Abstract

This work explores the effects of 60Co and 137Cs γ-irradiation on the Photovoltaic parameters of mono-crystalline silicon solar cells. Two suitable (light source- solar cell) geometry were instrumented. They consist of a halogen lamp of 500W power and 100mW.cm-2 light intensity, and a mono-crystalline silicon solar cell with an active area of 10cm×5cm for each geometry. At room temperature, the forward bias (I-V) and (P-V) characteristics were determined under illumination, before and after irradiation with different 60Co γ-exposure doses; 532 mR, 1064 mR and 1596mR, for the first solar cell and different 137Cs γ-exposure doses; 280 mR, 560 mR and 837mR for the second cell for 1hr,2hrs, 3hrs , respectively. The results demonstrated that γ-exposure doses have a significant effect on the photovoltaic parameters and it controls the quality and performance of the solar cell. The open circuit voltage (Voc), short circuit current (Isc), maximum output power (Pm), fill factor (FF) and efficiency (η) are found to be decreased with different gamma exposure doses. For 60Co γ-exposure the Vm values were decreased by 0.4%, 2.9% and 9%, respectively while Im values were deteriorated by 9.7%, 12% and 17.5%, respectively. Consequently, the Pm values were deteriorated by approximately by 10%, 14.5% and 24.9%, respectively. The Voc and Isc values were deteriorated by approximately by 1.5%, 2.2% and 3% for Voc, and 3%, 6% and 11.9% for Isc, respectively. On the other hand, the FF values were deteriorated by approximately 5.9%, 7.1% and 12.2%, while the η values deteriorated by 9%, 13.4% and 24% respectively. Similarly For 137Cs γ-exposure the Vm values were decreased by 0.4%, 2.9% and 9%, respectively while Im values were deteriorated by 7.9%, 10.1% and 13.3%, respectively. Consequently, the Pm values were deteriorated by approximately 8.3%, 12.8% and 21%, respectively. The Voc and Isc values were deteriorated by approximately 0.9%, 1.6% and 2% for Voc, and 2%, 5% and 10.9 % for Isc, respectively. On the other hand, the FF values were deteriorated by approximately 5.5%, 6.8% and 9.7%, while the η values deteriorated by 7.1 %, 11.7% and 20.2% respectively. When the reduction of the I-V characteristics caused by 60Co γ-ray photons were compared with those caused by 137Cs γ-ray photons at the same acquisition time (1,2,3 hours) , it was found that the Vmp reduction caused by 60Co γ-ray photons exceeds that of 137Cs γ-ray photons by 0.04% , 0.0001 % , 0.001% respectively .while the Imp reduction caused by 60Co γ-ray photons exceeds that of 137Cs γ-ray photons by 1.96% , 2 % , 4.9 % respectively . On the other hand when comparing the P-V reduction caused by 60Co γ-ray photons with that caused by 137Cs γ-ray photons at the same acquisition time (1,2,3 hours) for both sources, it was found that the Pmp reduction caused by 60Co γ-ray photons exceeds that of 137Cs γ-ray photons by 2% 1.9% and 4.7% respectively .This may attribute to the fact that the average energy of 60Co (1.25 MeV) is higher than the energy of 137Cs (0.662 Mev). The results re-confirmed the deterioration effect of induced 60Co and137Cs γ displacement damage on the photovoltaic parameters of mc-Si solar cell