Progress in the development of high-conversion-efficiency a-Si/μc-Si tandem solar module using μc-Si thin film with high deposition rate on Gen. 5.5 large-area glass substrate
The technology to make high-quality, high-reliability solar modules with a high deposition rate for μc-Si thin-film is a problem for the industrialization of low-cost, high-conversion-efficiency a-Si/μc-Si tandem structure solar modules. Sanyo has solved this problem by developing an original CVD technique called Localized Plasma Confinement CVD and a new evaluation method for μc-Si thin film. A stabilized conversion efficiency of 10.0% was achieved for an a-Si/μc-Si tandem structure solar module, and a deposition rate of 2.4 nm/s for μc-Si thin-film was attained on a Gen. 5.5 full-size glass substrate. To obtain a higher conversion-efficiency a-Si/μc-Si tandem structure solar module, fundamental studies of μc-Si thin-film have been performed, and a stabilized conversion efficiency of 10.5% (Initial solar module conversion efficiency: 12.0%) has been achieved on a large-area glass substrate. Furthermore, in the study of this development, the highest stabilized conversion efficiency of 12.0% (Initial conversion-efficiency: 13.5%) was attained. Module reliability tests confirmed by IEC 61646 Ed. 2 revealed that the performance of the module is adapted. These high-performance a-Si/μc-Si tandem structure solar modules were prepared by using the knowledge of our thin-film and module technologies.
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.
Microcrystalline silicon.. Growth and device application
Abstract Processes used to grow hydrogenated microcrystalline silicon (μc-Si:H) from a H 2 /SiH 4 -glow discharge plasma are explained in comparison to those for hydrogenated amorphous silicon (a-Si:H). Differences and similarities between μc-Si:H and a-Si:H-growth reactions in the plasma and on the film-growing surface are discussed, and the nucleus-formation process followed by epitaxial-like crystal growth process is illustrated as unique processes for the formulation of μc-Si:H. Determination of the effect of dangling-bond defect density on the propagation of the resulting μc-Si:H films is also discussed in parallel with the effect on a-Si:H in order to obtain a clue to improve opto-electronic properties of those materials for device applications especially for thin-film-silicon solar cells. Material issues to produce low cost and high efficiency solar cells are described, and finally recent progress in those issues is demonstrated.