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

Abstract Cu 2 MSnS 4 (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 Cu 2 MSnS 4 (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 TiS 2 /Cu 2 MSnS 4 (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 TiS 2 ‐based solar cells, providing valuable insights for the photovoltaic community.