Theoretical Insights and Numerical Simulation of CdS/CuInS ₂ Heterojunction Solar Cells for Enhanced Performance Analysis

Abstract

This study investigates the performance of CdS/CuInS <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">${}_{2}$</tex> heterojunction thin-film solar cells through numerical simulation, focusing on how the properties of the electron transport layer (ETL) influence device behavior. Using SCAPS-1D modeling, we examined the effects of ETL band gap, conduction-band offset (CBO), electron affinity, and temperature on key device parameters such as the open circuit voltage (Voc), short circuit current density (Jsc), fill factor (FF), and overall efficiency <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(\eta)$</tex>. The results show that adjusting the ETL's band gap and electron affinity can establish a more beneficial band alignment at the CdS/CuInS <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">${}_{2}$</tex> junction, which suppresses carrier recombination and improves charge extraction. An appropriately shaped spike-type CBO was found to reduce electron backflow without hindering forward transport. In addition, the temperature-dependent simulations reveal that cell performance degrades as the operating temperature increases: The open-circuit voltage decreases noticeably with temperature, falling from 0.85 V at 200 K to 0.52 V at 400 K, while <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\eta$</tex> decreases from 15.35% to 7.42%. These results offer practical insight for improving the design of CuInS <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">${}_{2}$</tex>-based solar cells and deepen the theoretical understanding needed to achieve high-efficiency, thermally stable devices.