Analysis of Si/SiGe Heterostructure Solar Cell

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 of heterostructure solar cell. The research has investigated characteristics such as short circuit current density ( ), generation rate ( ), absorption coefficient (α), and open circuit voltage ( ) 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. 1. Introduction The development of new energy sources is continuously being enhanced because of the critical situation of the nonrenewable resources. Thus, the renewable energy sources have become a more important contributor to the total energy consumed in the world. Sun provides enormous amounts of energy, powering oceans as well as atmospheric currents and cycle of evaporation. Electricity from solar energy is one of the most unprecedented cost effective methods of electricity production. Japan is leading with 64% electricity production using photovoltaic solar cell as shown in Figure 1. The solar cells have considerably reduced the cost/watt of produced electricity by a factor of 5–10 to compete with fossil and nuclear electricity and by a factor of 25–50 to compete with primary fossil energy [1]. Therefore, solar energy is one of the attractive types of renewable sources of energy replacing fossil fuels due to its profusion. In fact, the demand for solar energy has increased over the past 20 years. The market for PV systems is growing worldwide. In fact, nowadays, solar PV provides around 4800？GW. The sun continuously supplies about 1.2 × 1025 [1] terawatts of energy which is greater than any other renewable or nonrenewable sources of energy. Solar cell is generally constructed using crystalline silicon (c-Si) which has absolutely low absorption coefficient because of its indirect band structure; therefore, it is less preferable for solar technology. Here alloy of SiGe is considered due to its low energy band gap and increase in absorption coefficient as compared to Si. Figure 2 shows the