Enhancement of solar cell performance with the Pb incorporation in CdS quantum dots

Quantum Dot Solar Cells (QDSCs) are gaining popularity among third generation solar cells due to their unique features and non-conventional properties. However, systematic studies are sparse in the literature. In this work, we report on systematic investigations on the various interfaces of large area CdS-based QDSCs as well as how Pb incorporation in CdS as a ternary alloy improved the performance of solar cells. The inclusion of Pb into CdS has increased the absorption and extended it to the infrared region, while the recombination of charge carriers was reduced. Electrical impedance spectroscopy measurement was used to study and analyze the influence of Pb incorporation on charge transport phenomenon at the interfaces of QDSCs. It was found that solar cells with 7.2% Pb performed significantly better. The addition of Pb to CdS leads in a threefold improvement in solar cell efficiency (η = 2.0%) with a high open-circuit voltage (V_OC) of 0.758 V in 1 cm² area devices as compared to CdS solar cells (η = 0.6%, V_OC = 0.489 V). The effect of counter electrodes on PbCdS solar cells was investigated, and it was found that Carbon fabric counter electrode devices have better efficiency of, η = 2.9% when compared to Pt (η = 0.1%) and Cu₂S (η = 2.0%) counter electrodes. Our devices (1 cm² area) have shown stability and reliability in J–V characteristics and efficiency even after two months of storage at ambient conditions. This study clearly demonstrates that ternary alloyed quantum dots with suitable counter electrodes are beneficial for the efficient QDSCs.