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Japanese scientists have developed a wide-bandgap chalcopyrite solar cell that can reportedly achieve high open-circuit voltage and fill factor values. The device is intended for use in top cell applications in tandem devices.
Scientists from the National Institute of Advanced Industrial Science and Technology (AIST) in Japan have fabricated a wide-bandgap thin-film solar cell based on an indium-free chalcopyrite (CuGaSe2 or CGSe) absorber.
CuGaSe2 has an energy bandgap of 1.7?eV. It has been used in solar cells with limited fill factor and open-circuit voltage to date. “We utilized techniques that can realize the simultaneous achievement of high open-circuit voltage and fill factor values,” the researchs lead author, Shogo Ishizuka, told pv magazine. “Our wide-gap chalcopyrite cell could be used for top cell applications in tandem devices.”
The research group stressed that, in its previous studies, the incorporation of aluminum (Al) in CuGaSe2 thin films led to degradation rather than enhancement of solar cell performance. However, it found that the incorporation of a very small amount of aluminum (Al) in the backside region of CuGaSe2 films is effective in enhancing the cells open-circuit voltage, fill factor and efficiency. “This result is mainly attributable to the formation of a back-surface field (BSF) which enhances minority carrier collection,” it stated.
The academics built the cell with a substrate made of soda lime glass (SLG) coated with molybdenum (Mo), a back contact, an indium-free chalcopyrite absorber, a 110 nm cadmium sulfide (CdS) buffer layer, a window layer of zinc oxide (ZnO), and a grid electrode. |
