CdTe/CdS heterojunction Solar Cell suitable for Low-Illumination Applications

Abstract

CdTe is a very robust and chemically stable II-VI class semiconducting material and for this reason its related solar cell thin film photovoltaic technology is now the only thin film technology in the first 10 top producers in the world. CdTe has a band gap of about 1.5 eV which is optimum for the Schockley-Queisser limit and could deliver very high theoretical efficiency of single junction device of more than 32%, with an open circuit voltage of 1 V and a short circuit current density exceeding 30 mA/cm2 CdTe solar cells were introduced at the beginning of the 70s and have been thoroughly studied and implemented in the past 30 years. A simple structure of CdTe/CdS heterostructure photovoltaic device, in which CdTe acts as an active layer and CdS as buffer later has been optimized by SCAPS-1D software to study the effect of operating temperature, absorber and buffer layer thicknesses and work function of contacting metals at the two ends of the PV device at very low incident power. This study is very helpful in building an efficient and cost effective solar cell for portable electronic devices such as portable computers and cell phones that work at low incident power because most of such devices work at diffused and reflected sunlight. In this research, we simulated a basic CdTe PV cell with a high efficiency at extremely low incident power. In this paper we have systematically investigated the effect of temperature, work function and absorber layer thickness on solar cell efficiency. Device efficiency decreases on increasing the temperature. For work function between 5.7 eV and 6.35 eV, various device characteristics remain almost constant. Increasing thickness of main absorber layer CdTe beyond 500 nm has no significant effect on the efficiency of the device.