Remarkable progress in thin-film silicon solar cells using high-efficiency triple-junction technology

• Published in: Solar energy materials and solar cells 2013-12, Vol.119, p.26-35
• Main Authors: Kim, Soohyun, Chung, Jin-Won, Lee, Hyun, Park, Jinhee, Heo, Younho, Lee, Heon-Min
• Format: Article
• Language: English
• Subjects: Amorphous silicon; Doping; Microcrystalline silicon; Microcrystalline silicon oxide; Photovoltaic cells; Silicon; Silicon oxides; Solar cells; Stabilized efficiency; Stacks; Thin films; Thin-film silicon solar cell; Triple junction; Utilization
• ISSN: 0927-0248; 1879-3398
• DOI: 10.1016/j.solmat.2013.04.016

Despite the many advantages of thin-film silicon (Si) solar cells, their low efficiencies remain a challenge that must be overcome. Efficient light utilization across the solar spectrum is required to achieve efficiencies over 15%, allowing them to be competitive with other solar cell technologies. To produce high-efficiency thin-film Si solar cells, we have developed triple-junction solar cell structures to enhance solar spectrum utilization. To maximize the light management, in-house ZnO:Al layers with high haze ratios and high transmittances were developed. In addition, novel doping layers, such as n-type microcrystalline silicon oxide (µc-SiOx:H), which has a very low refractive index, and p-type microcrystalline silicon oxide (µc-SiOx:H), which has a wide bandgap, were successfully applied to the optical reflector and the window layer, respectively. Thin-film quality control techniques for the deposition of hydrogenated amorphous silicon (a-Si:H) in the top cell, hydrogenated amorphous silicon-germanium (a-SiGe:H) or hydrogenated microcrystalline silicon (μc-Si:H) in the middle cell, and hydrogenated microcrystalline silicon (μc-Si:H) in the bottom cell were also important factors leading to the production of high-efficiency triple-junction solar cells. As a result of this work, an initial efficiency of 16.1% (in-house measurement) in the a-Si:H/a-SiGe:H/μc-Si:H stack and a stabilized efficiency of 13.4% (confirmed by NREL) in the a-Si:H/μc-Si:H/μc-Si:H stack were successfully achieved in a small-area triple-junction solar cell with dimensions of 1cm×1cm.