Analyzing Si-SiGe thin-film solar cell by simulation and calculation

One of the solutions to the serious crisis of global warming and energy shortage is the renewable energy sources. Solar cell is one of the most promising sources of renewable energy. In the frame of the thin-film solar cell, the reduction for the active cell thickness and the improvement for the solar cell efficiency both are very important from an applied point of view. In order to avoid a reduction of the short circuit current (Jsc) in a small cell thickness, it is necessary to increase absorbability of the material and optimize the cell structure. The use of a lower band gap material such as SiGe in the active region in the cell is a possible candidate, given their compatibility with the mature Si based cell process. The increase of Jsc in the small band gap SiGe material, owing to the increased absorption, is highly expected. However, a drop of the open-circuit voltage (Voc) is another issue, which also needs to be avoided, owing to the increase of the intrinsic carrier concentration in the SiGe layer with smaller material band gap. Therefore, the optimal structure and process design for high efficient SiGe solar cell still remains an open question. In this work, the designed experimental conditions are compared qualitatively with the theoretical calculation and further demonstrate the optimal SiGe solar cell structure, considering related parameters such as Jsc, Voc, and fill factor (FF). The operated temperature sensitivity and its dependency with the solar cell efficiency for the SiGe and Si solar cell are also understood for the real application and it will also be investigated in this work.