부산대학교 도서관

We fabricate semitransparent ultrathin (STUT) Cu(In,Ga)Se (CIGSe) thin film solar cell on indium-doped tin oxide (ITO) substrate by using single-stage co-evaporation process. The CIGSe absorption layer is deposited with a thickness of 300 nm, which is much thinner than the usual non-transparent thickness of 2 μm, to be applied to a transparent type. However, the reduced thickness of STUT CIGSe absorber layer leads to the reduction of electron and hole collection efficiency at the front and back side. Hence, it is necessary to improve the interface quality at the heterojunction. An engineered Zn-based buffer structure consisted of a few nanometer ZnS passivation and ZnMgO (ZMO) buffer layer is suggested and deposited on STUT CIGSe absorber using Atomic Layer Deposition (ALD). Compared with Chemical Bath Deposition (CBD) to deposit the widely used conventional Cadmium Sulfide (CdS) buffer layer, ALD is more advantageous to control the thickness and composition of buffer layer. In this study, we change the Zn/Mg ratio of ZMO buffer in STUT CIGSe solar cell structure, while maintaining other conditions unchanged. The STUT CIGSe solar cells with Zn/Mg ratio of 3:1 in ZMO buffer layer exhibit much higher power conversion efficiencies compared to a reference solar cell sample with a CdS buffer. The properties of the ALD-grown thin films and photovoltaic performances of solar cells are characterized by utilizing field emission scanning electron microscope (FE-SEM), external quantum efficiency (EQE), and a solar simulator providing AM1.5 spectrum. Details of STUT CIGSe solar cells with ZMO buffer layer will be discussed with the related analysis results based on comparison with the reference cell.