Damage Effects And Simulation On High Efficiency TJ-GaAs Solar Cells Under Radiation Environment

Nowadays three junctions(TJ) solar cells have conversion efficiency as high as 30% after procedure and configuration optimization, which is being the major products used in space. Using a ground-based space-environment simulator and some complementary techniques to characterize solar cells, the behaviors of degradation of two kinds of high efficiency solar cells were studied. The mechanism of degradation of the irradiated solar cells was studied using photoluminescence(PL) and time-resolved photoluminescence(TRPL). Based on experiments, TJ-solar cells were modeled by PC1 D software, which help provide theoretical basis to design of the procedure and configuration, and irradiation damage evaluation of the TJ solar cells.The results indicate that, 1 Me V electron irradiation would results in homogenerous damage in the whole TJ-solar cells, but the middle Ga As sub-cell shows more vunlerable to the irradiation. Protons caused more serious damage than electrons irradiation. Due to the smaller range in the solar cell for lower energy protons, 70 ke V proton irradiation causes damage and electrical property degradation only in the top Ga In P sub-cell, while 150 ke V proton irradiation could damage both of the top Ga In P and middle Ga As sub cells, thus causing more serious degradation of TJ solar cells. In this case, the degradation models of electrical properties for two kinds of solar cells—11BP734 and 12 GPB were established. Based on the above-mentioned results and solar cell simulations, it was found that compared with 11BP734-type TJ solar cells, 12 GPB solar cells shows better stability in irradiation environment and higher efficiency just due to special configuration designs such as thinner base region and back reflection layer in the correspongding sub-cells.High energy electrons and protons cause diaplacement damage effects within the particle ranges, leadding to decrease of quantum efficiency and fluorescence efficiency of the cells. Comparatively, low energy protons would led to more obvious decline. From photoluminescence and time-resolved photoluminescence spectra, it can be detected the decrease of lifetime of minority carriers in the corresponding sub-cells. Calculation of lifetimes of minority carriers indicates that 12 GPB shows more resistant to irradiation.On the basis of the abovementioned results and an open PC1 D code, some models were established to simulate the behaviors of solar cell in the states of as-received, homogeneous and in-homogeneous damage. The simulated results indicate that lifetime decrease of minority carriers in a single-junction solar cell will cause obvious changes of energy band structure and electrical currents, furthermore changing the output electrical properties of the cells. For TJ solar cells, circuit simulation could be used to calculate the I-V curves based on the principle of current limitation and series voltage feature. By PC1 D software and circuit analysis, the damage effect of space radiation environment, lifetime of minority carriers and the output electrical properties of the TJ solar cells are connected together, which would be used to predict the electrical properties of solar cells of three or more junctions in space environment.