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Sai H.,Japan National Institute of Advanced Industrial Science and Technology | Maejima K.,Photovoltaic Power Generation Technology Research Association | Maejima K.,Kagoshima University | Matsui T.,Japan National Institute of Advanced Industrial Science and Technology | And 7 more authors.
IEEE Journal of Photovoltaics | Year: 2015

Power conversion efficiency of thin-film microcrystalline silicon solar cells has been remarkably improved recently: from 10.1% to 11.8%. Front transparent conductive oxide (TCO) films have played an important role in this efficiency improvement. In this study, the impact of the front TCO films was investigated by comparing microcrystalline silicon solar cells with In2O3:Sn films grown by sputtering and ZnO:B films grown by metal-organic chemical vapor deposition (MOCVD). Improvement mechanisms in open-circuit voltages and fill factors in solar cells are investigated and discussed. © 2011-2012 IEEE.


Sai H.,Japan National Institute of Advanced Industrial Science and Technology | Saito K.,Photovoltaic Power Generation Technology Research Association | Kondo M.,Japan National Institute of Advanced Industrial Science and Technology
Conference Record of the IEEE Photovoltaic Specialists Conference | Year: 2012

Periodically textured back reflectors with a honeycomb dimple pattern are investigated for improving the infrared response and conversion efficiency in substrate-type microcrystalline (μc-Si:H) silicon solar cells. For 1-μm-thick μc-Si:H cells, the best current density is obtained at the period of 1.4 μm, while a substantial enhancement in the external quantum efficiency is achievable in a wide range of period of 1-2 μm. In addition, photocurrent of the cells is improved with increasing the aspect ratio of the honeycomb textures. As a result of a high open-circuit voltage and fill factor, as well as the improved current densities, high conversion efficiencies of 9.4% and 9.9% are realized in the 1-μm-thick and 2-μm-thick μc-Si:H cells, respectively. © 2012 IEEE.


Maejima K.,Photovoltaic Power Generation Technology Research Association | Koida T.,Japan National Institute of Advanced Industrial Science and Technology | Sai H.,Japan National Institute of Advanced Industrial Science and Technology | Matsui T.,Japan National Institute of Advanced Industrial Science and Technology | And 3 more authors.
Thin Solid Films | Year: 2014

Boron-doped zinc oxide films were fabricated by metal-organic chemical vapor deposition at deposition temperatures (Td) from 150 to 210 °C. The deposition rate increases abruptly and monotonically with increasing Td. The resistivity also varies drastically, and a minimum resistivity of 1.6 × 10- 3 cm is obtained at Td = 175 °C. The crystal orientation and surface texture show Td dependence. These characteristics correlate with each other. The dependence of these characteristics on Td is caused by the reactivity of the source materials. © 2013 Elsevier B.V.


Morita H.,Photovoltaic Power Generation Technology Research Association | Morita H.,Toray Industries Inc | Miyashita M.,Toray Industries Inc | Masuda A.,Japan National Institute of Advanced Industrial Science and Technology
Japanese Journal of Applied Physics | Year: 2015

This work focuses on investigating the degradation factor for organic photovoltaic (OPV) modules. We established the composition of a test module that has suitable barrier properties against moisture ingress using the Ca method. Then, we mounted an OPV cell in the test module and conducted durability tests. We determined in reliability tests that the main degradation factors for OPV modules are products from encapsulants. Then, we added a vacuum process to the sample preparation procedure. We conducted durability tests on the OPV module prepared by the improved process, and we observed a change in the pattern of degradation. We concluded that the vacuum process affected the degradation mechanism. © 2015 The Japan Society of Applied Physics.

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