Work Function of Metal Back Contact Surface Alloy Molybdenum (Mo) With Tungsten (W) For Copper Indium Gallium Selenide (Cigs) Thin Film Solar Cell: Simulation Using Scaps-1d And Density Functional Theory (Dft) Using Winmostar Quantum Espresso

Abstract

The rapid growth in today’s electronic technology and usage leads to a high demand of electrical power consumptions. Researchers around the globe are continuing finding for renewable sources of energy to meet the increasing demands of energy. This is because the high fossil fuel and carbon consumptions contribute greatly on the emissions of carbon dioxide (CO2) and other greenhouse gases which have become the primary contributor of global climate change. Global temperatures have risen sharply over the last few decades and the atmospheric concentrations of CO2 continue to rise while the global emissions have not yet peaked [1]. Research and development of CIGS solar cells was started in 1980s as one of the various renewable sources of energy. CIGS thin film solar cells efficiency remains become an interesting topic among the researchers. University of Maine achieved 5.8% CIGS thin film solar cells efficiency in 1976. The efficiency has significantly improved since then to 23.6% in 2023 by Evolar/UU [3]. This study aims to improve the efficiency by focusing on the metal back contact of the CIGS thin film solar cells. The simulations were conducted using SCAPS-1D and Winmostar Quantum Espresso for quantum chemical, molecular dynamics and first-principles calculations simulation tools. Back contact layer of CIGS solar cell acts as an optical reflector to reflect light back to the absorber layer. Molybdenum (Mo) is commonly used as the back contact because it forms low resistivity ohmic contact to CIGS absorber layer and has high conductivity. Furthermore, its conductivity does not degrade during deposition of CIGS at high substrate temperature, and it does not react strongly, chemically, with CIGS absorber layer. However, work function property of Mo is within the range of 4.36 eV to 4.95 eV. There is a need to increase the work function property of the back contact to improve carrier collection near the back contact. The findings from the study offers a critical insight into factors that could further improve the CIGS solar cells efficiency.