Degradation mechanism of concentrator solar receivers without protection layer

GaInP/GaInAs/Ge triple junction concentrator solar receivers without protection layer were conducted sequentially at 90, 110, 130 and 150 °C for 25, 30, 30 and 50 h, respectively. After the step stress accelerated degradation tests (SSADT), gradual degradation in the dark and light I-V characteristics were observed. Degradation of devices results in the decrease of open-circuit voltage (Voc), fill factor (FF) and efficiency. The degradation mechanism of these triple junction concentrator solar receivers is attributed to the recombination current in the depletion region at the chip perimeter of solar cells. The mean time to failure (MTTF) of 380 h at 65 °C and active energy (Ea) of 0.16 eV were obtained by the statistical analysis with cumulative damage and exponential mode. Both of the obtained values of MTTF and Ea are low, and this results might be possibly due to our devices being without encapsulated protection layer.