Analysis of Si/SiGe Heterostructure Solar Cell

Abstract

Sunlight is the largest source of carbon-neutral energy. Large amount of energy, about 4.3 × 1020 J/hr (Lewis, 2005), is radiated because of nuclear fusion reaction by sun, but it is unfortunate that it is not exploited to its maximum level. Various photovoltaic researches are ongoing to find low cost, and highly efficient solar cell to fulfil looming energy crisis around the globe. Thin film solar cell along with enhanced absorption property will be the best, so combination of SiGe alloy is considered. The paper presented here consists of a numerical model ofSi/Si1-xGexheterostructure solar cell. The research has investigated characteristics such as short circuit current density (Jsc), generation rate (G), absorption coefficient (α), and open circuit voltage (Voc) with optimal Ge concentration. The addition of Ge content to Si layer will affect the property of material and can be calculated with the use of Vegard’s law. Due to this, short circuit current density increases.

MATLAB User Interface for Simulation of Silicon Germanium Solar Cell

“…Therefore, it depends on the saturation current which may vary up to a significant margin. When mole fraction is increased, energy band gap of SiGe slopes down, which results in the increase in saturation current ( ), as explained in [9] and as shown in Figure 9. Therefore, the combined effect of saturation current and short circuit current results in the decrease in the value of oc when mole fraction is increased.…”

“…SiGe alloy layer is a tunable absorber layer, suitable for construction of efficient and optimized solar cell. According to [9], time for extraction of data was long, but, for this user interface, the result computation time is less. This GUI can be used to optimize the following Si 1− Ge parameters: (a) properties variation with variable layer thickness; (b) effect on electrical and structural properties under variation of temperature.…”

“…Developed numerical model [9]: thin layer of highly doped n-Si is constructed with a dimension of 5 × 10 −9 m as a capping layer to increase luminescence efficiency. Alloy of silicon germanium is used in this layer and thickness SiGe is 50 × 10 −9 m. Final layer is p-type doped silicon layer with thickness Si = 100 × 10 −9 m. The model is designed in such a way that numerical cell is represented in the form Si 1− Ge , where is the mole fraction of germanium which varies from = 0, that is, pure silicon, until = 1, that is, pure germanium, as shown in Figure 4.…”

“…To compute different properties of alloy of silicon germanium, we need to analyze both semiconductors individually. To combine the effect of both semiconductors, Vegard's law is used, and this can be represented as [9] …”

“…For the calculation of the total generated photocurrent, the program calculates the conduction current density due to holes and diffusion current density due to electrons and drift current density with the help of the equation in [9]. Current density at different Ge mole fraction is plotted as a function of voltage.…”