TiO2 as an intermediate buffer layer in Cu(In,Ga)Se2 solar cells
Date
2020
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Publisher
University of Delaware
Abstract
As demand for renewable energy, specifically solar energy, increases, there is an increased interest on better conversion devices and materials. With thin film solar cells using CIGS (Cadmium – Indium – Gallium - Sulphide) and CIS (Cadmium-Indium-Sulphide) as the absorber layer, CdS (Cadmium Sulphide) is most often used as the buffer layer, which is toxic. The motivation of this thesis is to find a promising replacement for the toxic CdS material. The performance of a solar cell using TiO2 as the buffer layer is shown with both absorbers. This performance is compared to the commonly used solar cells that use Cds/ZnO (Zinc Oxide) as buffer layers. The advantages of the TiO2 (Titanium Dioxide) material over CdS material are discussed. The I-V curves of the fabricated solar cells are compared with the simulated curves using the same material parameters. SCAPS (a Solar Cell Capacitance Simulator) simulation program was used for simulation and the material properties used for each layer of the cell are explained. A simulation model was successfully developed in accordance with the experimental model of the new design of the cell. In this thesis, we conclude that TiO2 used as buffer layer for a CIGS/CIS cell is a potential replacement for CdS buffer layer. A comparison of cells using CIGS and CIS buffer layers shows that higher efficiencies were obtained when the Gallium (Ga) content in the material was 0 (CIS cell). Further studies can be done to improve the performance by varying the Ga content to modify the CIGS material and effectively improve the performance.
Description
Keywords
Buffer layer, CIGS, Solar cell, TiO2