7. Solar Cell Fabrication and Characterisation

This chapter provides an insight into next-generation graded bandgap photovoltaic device fabrication. All-electrodeposited devices were fabricated using n-p, n-n-p, n-n + large Schottky barrier (SB) and n-n-n + SB architecture using ZnS, CdS and CdTe thin layers. The fabricated devices were evaluated using both current-voltage (I-V) and capacitance-voltage (C-V) techniques. The inclusion of Ga into the regular CdCl₂ post-growth treatment and the effect of pH were also explored with the improved result as compared to the regular CdCl₂ PGT. Based on all experimental findings as explored within the limit of this work, the most promising of the configurations examined are the glass/FTO/n-CdS/n-CdTe/p-CdTe/Au with thicknesses of 120 nm (n-CdS), 1200 nm (n-CdTe), 30 nm (p-CdTe) and 100 nm (Au). The highest conversion efficiencies observed for two separate batches were 15.3 and 18.4%. The devices with the 18.4% efficiency showed some instability and therefore require further investigation. The glass/FTO/n-ZnS/n-CdS/n-CdTe/Au configuration with thicknesses of 50 nm (n-ZnS), 65 nm (n-CdS), 1200 nm (n-CdTe) and 100 nm (Au) also shows promising results with the highest efficiency achieved being 14.1% owing to bandgap grading strengths.