Influences of Morphology of Window Layer on the Characteristics of PbS Quantum Dot Solar Cells

Background: In QDs-based solar cell devices, the PbS QDs layer was mainly focused to optimize. The ZnO electron acceptor layer attracts less attention whereas it shows the key roles in extracting and transporting charge carriers in heterojunction. The utilization of 1-D ZnO structures has been demonstrated to be large interface areas and good carrier pathways for efficient carrier collection. However, the influences of the morphology of metal oxide nanostructures on the photovoltaic performance of QD-based solar cells have been few in-depth reports. Objective: In this work, ZnO NRs/PbS QD based solar cells were fabricated. The influences of the ZnO NRs array structures on characteristics of ZnO NRs/PbS QD based solar cells were investigated. Method: ZnO NRs/PbS QD based solar cells were fabricated via spin coating method. XRD, SEM, UV-VIS-NIR spectrophotometer, I-V and EQE measurement systems were utilized to investigate the fabricated samples. Results: We have found optimum combinations of the linked parameters of ZnO NRs, their length of (230 ± 5) nm and density of (1.50 ± 5)x10¹⁰ # of rods.cm^-2, that exhibit maximum efficiency of ∼2.5% for the ZnO NR/PbS QDs based solar cell. Conclusion: The influences the ZnO NRs structures on the solar cell characteristics, including the absorption, external quantum efficiency, and current density-voltage curves, were investigated. There seems to be an optimum between NR length and their density for resulting in maximum efficiency. This could be due the interplay of solar flux absorption and junction area controlled by these two parameters of ZnO NR morphology.