Effect of Temperature on the Performance of Ga_0.84In_0.16As/Ge_0.93Sn_0.07 Double-junction Solar Cells

Based on the Varshni model-temperature dependence of the energy gap and the empirical Caughey-Thomas model, Ga_0.84In_0.16As/Ge_0.93Sn_0.07 double-junction solar cells under lattice matching were numerically simulated. In this study, the band gap E_g, reverse saturation current density J₀ of the materials and the photovoltaic properties on temperatures were explored detailedly. Results show that band gaps of the Ga_0.84In_0.16As and Ge_0.93Sn_0.07sub-cells decrease approximately linearly in the temperature range of 250-400 K with the rates of -0.412 meV/K and -0.274 meV/K, respectively. The J₀ of the subcell is exponentially enhanced as the material temperature increases. Temperature coefficients of J_sc and V_oc are about 12.86 μA/(cm²·K) and -3.48 mV/K, respectively. The FF decreases from 0.87 to 0.78, and the η reduces from 31.39% to 17.69% when the temperature increases from 250 K to 400 K. In addition, the temperature coefficients of the J_sc, V_oc, FF and η of the Ge_0.93Sn_0.07 sub-cells are about 6.59 μA/(cm²·K), - 1.76 mV/K, -0.213%/K and -0.042%/K, respectively, which are better than the temperature performance of the Ge sub-cells in the traditional Ⅲ-Ⅴ multi-junction cells. The results in the paper can be conducive to promote the low-cost development and application of GaInAs/GeSn-based multi-junction solar cells.