再生エネルギー研究センターパンフレット（英語）

10/20

9Photovoltaic Power Team－High-Performance PV Modules Based on Thin Crystalline Silicon Solar Cells－A large number of photovoltaic (PV) systems have been installed under Feed-In Tariff (FIT) since July 2012. In addition to the conventional installation on house rooftops, many large-scale power plants so called “mega solar” have been constructed. Reduction in PV power generation cost is very important to reduce the burden share of electricity users and to improve the competitiveness of PV modules in the market.Research Target　The team addresses the following subjects to develop technologies for producing low-cost, highly efficient and reliable modules (target conversion efficiency: 22%)●Silicon ingot slicing technology with high accuracy and reproducibility (thin wafer)●High efficiency cell fabrication technique using thin Si wafers (PERC cell、Back contact cell etc.)●Technologies for improving the efficiency and reliability of PV modules (development of new materials, structures, etc.)　The team is also focusing on the research of “smart stack technology” to develop a next-generation highly efficient solar cells (conversion efficiency higher than 30%). The technologies to achieve the power generation cost target of 14 JPY/kWh in 2020 and 7 JPY /kWh by 2030 will be developed.Research Outline　Though the crystalline silicon (c-Si) technology dominates the share in the PV-market, it requires significant cost reduction in order to accelerate the deployment of PV systems.　The team conducts comprehensive research using a semi-production line from ingot slicing to module fabrication and testing.●Thin wafer fabrication technology　The team is developing a slicing technology for thinner wafers with thicknesses of about 0.10 mm (from the present cell thickness of 0.18 mm to 0.08–0.10 mm).　The team also investigates the relationship between the cracks and the wafer strength to develop thin and tough wafers and to improve the yield during the cell processes such as the wafer cleaning.●Development of new cell fabrication techniques 　New cell production processes using the ion implantation technique have been developed in addition to the conventional thermal diffusion process. The effective use of the ion implantation can make possible the reduction of the number of cell processes during the back-contact cell fabrication.●Improvement in module reliability and development of a new evaluation method　A new nondestructive module evaluation method through the voltage mapping using the absolute electroluminescence (EL) method has been developed. A forward bias is applied to the solar cell and individual cell voltages can be evaluated from the luminescence intensity of the cells, and this technique is nondestructive.Japanese PV roadmap for 2030 (NEDO PV challenges)Equivalent to commercialelectricityEquivalent to generalpower sources23 JPY/kWh14 JPY/kWh7 JPY/kWh・Improvement in efficiencies and cost-down・Application of the technologies developed in the previous projects・Novel materials and structures・Application of novel technologies for mass-productionVoltage mapping by the absolute electroluminescence methodVoc (mV) representing evaluated valuesTotal intensity of luminescence (photons/s cm2)System (example)・Module efficiency: 25%・Utilization factor: 15%・Operation period: 30 yearsSystem (example)・Module efficiency: 22%・Utilization factor: 14%・Operation period: 25 yearsCost[JPY/kWh]201320152020202520300Figure of thinning process of wafer (cell)