Sodium incorporation effect on morphological and photovoltaic properties for Cu2ZnSnSe4 solar cells. (30th January 2020) - Tampo, Hitoshi
Abstract: The effects of sodium incorporation in Cu2 ZnSnSe4 (CZTSe) on morphological and photovoltaic properties were investigated as a function of the sodium supply. The sodium incorporation was found to significantly affect CZTSe grain growth, and the grain size increased up to μ m order from several hundred nm. No monotonic increase of the sodium concentration with NaF thickness was observed, and the sodium was pushed away from CZTSe bulk region at the grain growth. The carrier concentration decreased from the middle of 10 16 cm −3 to middle of 10 15 cm −3 with increasing NaF thickness, and the origin is discussed. The optimal NaF supply for the high conversion efficiency is shown, and the effect on the J – V curves were statistically analyzed using extracted device parameters. The improvement of the conversion efficiency was demonstrated to be due to the improvement of J sc and FF. It was found that FF improvement was strongly correlated to the shunt resistance and reverse saturation current density, and very weekly correlated to the series resistance. However, J sc was not so strongly correlated to these device parameters, and these phenomena are discussed.