Si0.7Ge0.3/Si SOLAR CELL BY OPTIMALLY THICKNESS OF GRADED Si0.7Ge0.3 LAYER

The thickness of graded Si0.7Ge0.3 layer will affect the absorption of solar light on the solar cell system. By increasing the absorption of solar light, achieved by lowering the thickness, this will increase the efficiency of solar cell device. Furthermore, optimum thickness graded-Si0.7Ge0.3 layer will contribute in economic aspect; on the other hand, this effort should not decrease the functioning of device itself. Consequently, reducing thickness of the cell will decrease the short circuit current. This can be prevented by using the lower-band gap material in the active base region of the cell. The potential candidate is SiGe alloy. In this paper we optimized the thickness of graded Si0.7Ge0.3 layer in order to minimize the defect dislocation due to the difference of lattice constant between Si and SiGe and also increase the efficiency of solar cell device. We investigate and analyze the effect of changing the thickness of graded Si0.7Ge0.3 layer by using simulation’s tools, i.e. pc1d version 5.8, and report the performance of this device, especially open circuit voltage, short circuit current, and fill factor which will affect the efficiency of device. In this paper, we will compare the performances of Si solar cell with graded-Si0.7Ge0.3, bulk Si0.7Ge0.3, and without Si0.7Ge0.3 layer.