Unraveling Spray Pyrolysis Mechanisms: Droplet Dynamics and Film Formation in CdTe Thin-Film Photocathodes

Aim: This review explores the mechanisms of spray pyrolysis for cadmium telluride (CdTe) thin-film photocathodes, focusing on droplet dynamics, nucleation processes, and film formation pathways relevant to photovoltaic and photocathode applications. Study Design: The study critically synthesizes recent literature from 2020 up to the time of manuscript submission, emphasizing its role in tailoring CdTe thin-film quality and performance. Methodology: A peer review of journal articles was conducted using databases including Google Scholar, Scopus, Web of Science, and ScienceDirect. Studies included examined droplet behavior, gas-to-particle and droplet-to-particle mechanisms, substrate conditions, and modeling approaches in spray pyrolysis, with a CdTe-specific context. Results: The review identifies two dominant pathways in film formation: droplet-to-particle (DTP), where precipitation occurs within droplets, and gas-to-particle (GTP), where vapor-phase nucleation predominates. Substrate temperature, precursor chemistry, atomizer type, and carrier gas flow were found to significantly influence film microstructure, crystallinity, and grain growth. Computational modeling, including evaporation kinetics, heat–mass transfer simulations, and nucleation-growth frameworks, provided theoretical grounding for experimental observations. These findings reveal the delicate balance between process parameters and the resulting CdTe film properties. Conclusions: Understanding spray pyrolysis mechanisms for CdTe thin films requires integrating droplet-scale dynamics with substrate-level interactions. The review highlights critical variables that can be tuned for optimal film quality and device efficiency, offering a guide for advancing flexible photocathodes and other next-generation energy devices. Future research should address the coupling of in situ diagnostics with advanced modeling to provide real-time control over film growth.