Copper salt engineering of CuInSSe thin films for high-efficiency solar cells

Abstract

This study systematically investigates how different copper precursors affect the structural, optical, electro- chemical, and electrical properties of spray-deposited CuInSe₂ (CISe) thin films. X-ray diffraction confirms single- phase, polycrystalline chalcopyrite formation without secondary phases. The copper precursor strongly in- fluences the microstructure, with CuI-derived films exhibiting the largest grain size (~0.55 μm), compared with Cu(NO₃)₂ (~0.28 μm) and CuCl₂ (~0.07 μm). All films show high absorption coefficients (>10⁴ cm⁻¹) in the 800–1100 nm range, indicating suitability as absorber layers. Mott–Schottky analysis confirms p-type conduc- tivity, with an optimal acceptor density of 2.4 × 10 ¹ ⁷ cm⁻³ for CuI-based films. Dark current–voltage mea- surements reveal ohmic behavior and the highest hole mobility (~2.1 × 10⁻² cm² V⁻¹ s⁻¹) for the CuI sample. SCAPS-1D simulations demonstrate that optimizing the ZnOS window layer improves band alignment, yielding a simulated efficiency of 17.28%, highlighting the potential of CuI-derived CISe films for efficient thin- film solar cells.