Exploring the impact of deposition pressure in CdTe thin film solar cells fabrication

Abstract

Cadmium Telluride (CdTe) is a potential material for thin-film solar cell fabrication due to its good optoelectronic characteristics, widespread availability, and inexpensive manufacturing costs. However, optimizing the deposition process to generate high-quality CdTe devices remains a challenge since deposition factors such as pressure have a substantial impact on the structural, optical, and electrical properties of the films, eventually influencing device performance. This study explores the effects of deposition pressure during the Close-Spaced Sublimation (CSS) process on the structural, morphological, optical and electrical characteristics of CdTe thin films, with an emphasis on pressures ranging from 1 to 10 Torr. High-quality CdTe films with large grain sizes (∼3 µm), cubic (111) preferential crystallite orientation, low dislocation density, and decreased strain are grown at deposition pressures ranging from 1.5 to 2 Torr, according to structural studies. These properties are appropriate for producing high-performance p-type CdTe absorber layers for solar cells. The optimized films has a band gap of 1.49 eV, a Voc of 0.64 V, a Jsc of over 18 mA/cm², and solar cell efficiencies above 5 % under normal AM1.5 conditions. Films deposited at higher pressures (≥5 Torr) exhibit poor electrical performance, including poorer carrier mobility, higher recombination losses, and low Jsc due to carrier dispersion and grain boundary defects. This work emphasizes the importance of deposition pressure in managing the balance of crystallinity, grain size, and carrier concentration, all of which are required for optimal solar cell performance. The findings present a systematic approach for optimizing CSS deposition parameters in order to achieve higher-efficiency CdTe thin-film solar cells. Furthermore, this study provides the groundwork for future research focusing on pressure-dependent manufacturing processes and post-deposition treatments to increase the efficiency, stability, and scalability of CdTe-based solar cells.