Advances, challenges, and perspectives in developing CuInX2 (X = S, Se) nanomaterials for solar energy conversion applications

Abstract

CuInX₂ (where X = S, Se) are among group I–III–VI's most recognized semiconductors in the ternary chalcogenides. These materials have come to the forefront of solar energy research owing to their optical and electronic properties, such as high absorption coefficients, tunable band gaps, and excellent thermal stability. This positions them as sustainable and low-cost alternatives for solar energy conversion devices. However, their practical implementation remains hindered due to several challenges, including low efficiencies associated with insufficient control in defect formation, variable stoichiometries, ligand selection, and binary or ternary compositional mixtures. A particularly limiting barrier is the current lack of understanding of the emission processes in these materials. Bringing these materials to light and their implementation in fabricating energy conversion devices will crystallize through overcoming these challenges. This review critically examines recent advances in the synthesis, characterization, and integration of CuInX₂ systems in solar energy-converting devices, highlighting current challenges and opportunities and offering insights that will not only accelerate research in this field but also contribute to the advancement of other ternary or quaternary copper-based chalcogenides.