<b>Effects of Chloride Doping on Optical Absorption in Spray-Pyrolyzed CdS Thin Films</b>

Abstract

Cadmium sulfide (CdS) thin films, vital window layers in optoelectronic devices like solar cells, face performance challenges from chloride impurities introduced via common spray pyrolysis precursors. This study investigates these impurities' effects on absorption properties by depositing undoped and chloride-doped CdS films on glass substrates at 303 K, 333 K, and 363 K using cadmium nitrate tetrahydrate and thiourea precursors. UV-Vis spectrophotometry revealed chloride-doped films exhibiting peak UV absorbance of 1.96 at 303 K surpassing undoped films' maximum of 1.90 at 333 K with progressive decrease across wavelengths (285-500 nm), indicating defect-mediated enhancements. SEM analysis confirmed superior compact, crack-free morphologies with uniform grains and reduced pinholes in 363 K doped films versus undoped counterparts. These findings demonstrate controlled chloride doping maximizes absorption and microstructural integrity, providing key insights for impurity-tailored deposition to elevate photovoltaic efficiency.