Quantum size effect of CdS quantum dot as electron transport layer for enhanced performance in CdTe based solar cells

Abstract

In this work a comprehensive experimental and theoretical investigation was carried out to examine the influence of the quantum size effect of CdS quantum dots (QDs) when employed as an electron transport layer (ETL) in PN-type CdTe-based solar cell. Although quantum dots have been extensively employed in the field of solar energy harvesting, their application as an ETL remains relatively under-investigated. In this work, CdS QDs were synthesized via the hot injection method, followed by thorough structural and optical characterization to determine critical material parameters required for accurate device simulation using SCAPS-1D. The study systematically examines the influence of varying QD sizes and the number of QD layers on the photovoltaic performance of the device. Additionally, optimization strategies involving the tuning of the thicknesses of the hole transport layer (HTL), ETL, and absorber layer were employed to further enhance the device efficiency. Simulation results reveal that the device performance is sensitive to both the size and distribution of QDs within the ETL. A maximum power conversion efficiency of 29.68 % was achieved with a single monolayer ETL configuration and an optimized QD size of 4.7 nm, whereas 16.5 % efficiency was reported for CdS as absorber layer previously. These findings underscore the pivotal role of quantum dot engineering in modulating charge transport and recombination dynamics, thereby offering valuable insights into the design of next-generation high-efficiency solar cells.