The Optimization of SiGe Hetero-Structure Thin-Film Solar Cell by the Theoretical Calculation and Quantitative Analysis

The characteristics of SiGe hetero-structure solar cell such as short circuit current density (Jsc), open-circuit voltage (Voc), fill factor (FF), and efficiency with optimal Ge concentration are investigated in this work. The average Ge concentration was systematically changed in the range from 0% to 30%. The appropriate addition of Ge in crystal Si solar cell is an effective way to increase the short circuit current density, without affecting on the open-circuit voltage, due to the modulation of the material band-gap and hetero-structure. Therefore, the solar cell efficiency can be further improved. With the optimization of Ge concentration and clean process condition, the overall efficiency of a Si_0.9Ge_0.1 solar cell is found to be improved about ~4% than it in the control Si solar cell. The band-gap of the SiGe material, the key parameter for the solar cell design, can be extracted by an Electron-Hole Plasma (EHP) model at different temperatures. Finally, the SiGe-based solar cell has also been observed that it has less operated temperature sensitivity than Si solar cell for the real application. The theoretical calculation and simulation in this work can help us to understand and engineer the high-efficiency SiGe solar cell qualitatively.