Quantifying Pinhole Defects in CdTe Thin Films for Solar Cell Applications

• Roselyn Anokye-Agyei, , Delaware State University

• William Shafarman, Electrical and Computer Engineering, University of Delaware

In recent decades, renewable energy has emerged as a global priority, with solar energy standing out as one of the most promising sources. Cadmium Telluride (CdTe) thin-film solar cells represent a cost-effective photovoltaic technology, but their performance can be limited by microscopic defects called pinholes that form during thin-film deposition. These localized voids in the solar cell absorber layer can create undesirable electrical pathways, known as shunt paths, which reduce overall device efficiency due to current leakage. This research investigated how different substrate cleaning methods influence the formation of pinholes in CdTe absorber layers. Substrates were prepared using varying cleaning protocols, followed by the deposition of CdSeTe thin films via thermal co-evaporation and CdTe films via vapor transport deposition. Digital photography, optical microscopy, and image analysis software were used to detect and quantify pinholes across multiple samples. Results showed that multi-step substrate cleaning was particularly effective in reducing pinhole density. This project provided valuable hands-on experience in substrate preparation, thin film deposition, and defect analysis. These findings underscore the importance of surface cleanliness and controlled deposition in producing high-quality absorber layers for efficient solar cell performance.