Identification of defective regions in thin-film Si solar cells for new-generation energy devices

We developed a high-conversion-efficiency, a-Si/μc-Si tandem solar module using μc-Si thin film on a Gen. 5 class glass substrate. The stabilized module efficiency was 10.7% (initial module efficiency: 12.0%). We prepared high-performance a-Si/μc-Si tandem solar cells based on our original technology for μc-Si thin films with localized plasma confinement chemical vapor deposition, optical confinement techniques, and laser patterning. To obtain higher conversion efficiency, optical confinement techniques are crucial, especially transparent conductive oxide (TCO) controlling technology. However, high-performance TCO includes steep valleys in the texture structure. Therefore, many defective regions are generated in the deposition of μc-Si thin film that degrade the solar cell performance. In this study we structurally identified these defective regions and propose a new formation model of the defective regions.