(1)Improvement of the performance of laboratory-scale CIGS solar cells
We have made a number of essential reasons clear which prevent the solar cells from achieving high efficiency and obtained laboratory-scale CIGS devices with efficiency of 22%. In addition, we have developed laboratory-scale indium-free CGS devices with efficiency of 11.0 %. These results strengthen the technological prospects of CIGS solar cells with high gallium concentration, which are expected as promising solar cells in the future.
(2)Development of CIGS submodules
We have developed CIGS submodules using soda lime sheet glass as substrates and have obtained efficiency of 20.3%. The technology developed here is an important elemental technology to improve the conversion efficiency of CIGS submodules, and hence can be applied to large area CIGS modules as well as flexible CIGS modules.
(3)Improvement of the performance of laboratory-scale CZTS and solar cells
We develop laboratory-scale CZTS solar cells using Ge-doped CZTSe (CZTGSe) system. As the results, we obtained high open circuit voltage of 0.527 V and conversion efficiency of 12.32% at the alloy composition ratio of Ge/(Ge+Sn) = 0.2.
(4)Development of the technology to characterize the electronic states by inversed photoemission spectroscopy
We develop new methods to characterize the electronic states of semiconductors for photovoltaics by combining both inversed photoemission spectroscopy and photoemission spectroscopy. We can characterize both the conduction band and valence band of the sample precisely by the method.
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