A CdS-Free Alternative TiS2 Buffer: Toward High-Performing Cu2MSnS4 (M = Co, Mn, Fe, Mg) Solar Cells

Abstract

Cu₂MSnS₄ (M = Co,Mn,Fe,Mg) are emerging as potential photovoltaic absorbers owing to their exceptional properties. However, a large open-circuit voltage (V_OC) deficit caused by the unfavorable band alignment with the toxic CdS buffer limits their overall efficiency. Therefore, identifying an appropriate alternative buffer is essential for improving performance. Herein, solar cell capacitance simulator in one dimension (SCAPS-1D) is employed to theoretically design and analyze these emerging solar cells using TiS₂ as a substitute for CdS. The investigation focuses on various parameters, including buffer, absorber, and interface characteristics, to evaluate their impacts on performance. Remarkably, the highest efficiencies achieved with TiS₂ buffers are 27.02%, 27.04%, 30.04%, and 30.26% for Cu₂MSnS₄ (M = Co,Mn,Fe,Mg), respectively, surpassing CdS by 1.36, 1.76, 1.23, and 1.15 times. The high efficiencies obtained are associated with reduced electron barrier of −0.24 eV, −0.4 eV, −0.04 eV, and 0.08 eV at TiS₂/Cu₂MSnS₄ (M = Co,Mn,Fe,Mg) interface, lower accumulation capacitance, significantly higher built-in potentials (>1.2 V), lower V_OC losses (<0.35 V) and improved recombination resistance in TiS₂ solar cells compared to CdS. Additionally, the study addresses the experimental challenges and strategies necessary for the practical fabrication of TiS₂-based solar cells, providing valuable insights for the photovoltaic community.