Establishing the hierarchy of growth-driven properties in CdS thin films and their role in CdS/PbS solar cell performance

Abstract

This study establishes a hierarchy of properties in CdS thin films synthesized through an ammonia-free chemical bath deposition (CBD) process with varying OH- content. By adjusting KOH volume added to the solution reaction, a progressive influence on film growth mechanisms was observed, resulting in systematic variations in thickness, morphology, stoichiometry, crystalline structure, and optical and electrical properties. These hierarchical changes directly impacted CdS/PbS solar cell performance. Thinner hexagonal CdS films, linked to low OH- content and ion-by-ion growth, enhanced cell efficiency by improving short-circuit current density (Jsc), while thicker films, with cubic structure, resulting from hydroxide-mediated growth at higher OH- levels, exhibited reduced resistivity and bandgap energy. Among these properties, film thickness emerged as the dominant factor influencing efficiency, followed by bandgap and electrical resistivity. Notably, Voc values of up to 620 mV were achieved, correlating directly with electron mobility, which reduces recombination losses. This hierarchical analysis underscores the pivotal role of OH- content in tailoring CdS film properties for enhanced CdS/PbS solar cell efficiency.