| 초록 |
To fabricate high performance thin film solar cells (TFSCs), CdS is widely used as an n-type buffer layer for various types of absorbers. CdS has a band gap of 2.4 eV that leads to a loss in the blue region of the solar spectrum, which could be potentially recovered by a more transparent layer. However, due to the toxicity of Cd, alternative buffer layer materials are needed. Zn(O,S) is a promising alternative buffer layer to CdS in Cu2ZnSn(S,Se)4 (CZTSSe) based solar cell due to its large bandgap and nontoxic elements. On the other hand, atomic layer deposition (ALD) technique is a great tool for the conformal deposition of a thin film with a precise thickness and desired stoichiometry. The deterioration of performance of CZTSSe thin film solar cell varies with secondary phases, interface defects, and band offset. Interface defects can be reduced through interface passivation. Dielectric materials such as TiO2, Al2O3, and Si3N4 deposited with ALD are mainly used. Interface passivation reduces the interface defect density, resulting in wider depletion widths and reduced interface recombination, contributing to VOC increase. CZTSSe / CdS interface passivation by TiO2, Al2O3 is also effective in CZTSSe thin film solar cell. In this study, we deposited Zn(O,S) as a Cd free buffer layer using ALD and deposited CdS using CBD method to fabricate a reference cell. In order to reduce the interface defect, the ZnS passivation layer was deposited using ALD before the Zn(O,S) buffer layer deposition, and the thickness of the ZnS passivation layer was changed to determine the effect on cell performance. |
