Abstract
Indium sulphide (InxSy) is a prominent candidate to be an alternative buffer layer to so-called toxic cadmium sulphide (CdS) in CIS based solar cells. In this study, buffer layer parameters layer thickness and buffer layer bandgap have been investigated by Solar Cell Capacitance Simulator (SCAPS) to find out the higher conversion efficiency. A promising result has been achieved with an efficiency of 16.76% (with V-infinity = 0.610 V, J(sc) = 34.63 mA/cm(2) and fill factor = 79.37) by using InXSy as a buffer layer. It is also found that the high efficiency of CIGS absorber layer thickness is between 1.5 mu m and 3 mu m. The bandgap of InxSy buffer layer was taken 2-2.9 eV to simulate which is related to the feasible value and InxSy bandgap is relatively higher compared to CdS buffer layer bandgap. Moreover, it is found that J(sc) is very high for the buffer layer thickness of 30-50nm and quantum efficiency is almost 80% in 350-500 nm region attributed to less absorption of light in the buffer layer. In addition, it is revealed that the highest efficiency cell can be achieved with the buffer layer bandgap of 2.74-2.90 eV. This result can be explained in the practical work as nonstoichoimetric composition of indium sulphide may result in different bandgaps. Hence, a specific non-stoichoimetry composition which results in the highest bandgap is desirable to achieve high efficiency InxSy-CIGS solar cells. From the simulation results, numerous influences of buffer layer are investigated in CIGS solar cell which can lead to the fabrication of high efficiency devices.