Improvement of Amorphous/Microcrystalline Silicon Tandem Junction Solar Cell

For thin film Silicon solar cells, conversion efficiency improvement and cost reduction are essential in order to compete to the other types of solar cells. ULVAC has been developed amoruphus silicon (a-Si)/microcrystalline silicon (μc-Si )tandem solar cells for the solution. We presented 1.1m x 1.4 m size a-Si/μc-Si tandem junction module with stabilized output power 145W (conversion efficiency 10% aperture area)[1][2]. In this work, development progress for higher conversion efficiency is reported. For further improvement, not only the quality-up of the absorber layers but also the effective light management are necessary. One of light management method is using inter layer between top cell and bottom cell. Light of shorter wavwlength is reflected to top cell by inter layer, and quantum efficency of top cell increases without thickening top layer thckness. Another method is light scattering by front electrode TCO. We have tested various materials and TCO deposition process to increase light trapping effect. Incorporating these technologies, we have achieved 10.8% conversion efficency by a-Si/μc-Si tandem solar cell with our developed TCO.