It was observed that the ionic conductivity of the solid-state electrolyte LiI/3-hydroxypropionitrile (HPN) = 1:4 (molar ratio) decreased dramatically with increasing iodine (12) concentration,which differs from the conduction behavior of the Grotthuss transport mechanism observed in liquid or gel electrolytes.The short-circuit photocurrent density (J_(sc)) of the dye-sensitized solar cell (DSSC) based on this electrolyte system increases with increasing I_2 concentration until LiI/I_2 is 1:0.05 (molar ratio).Beyond this limitation,the J_(sc) decreases.At low I_2 concentrations (I_2/LiI 0.05),the factors,including the increased light absorption by the I_3~-,the increased recombination of electrons at the photoanode with I_3~-,and the reduced ionic conductivity of the electrolyte,lead to a decrease of J_(sc).At the same time,the open-circuit voltage (V_(oc)) of the DSSC decreases monotonically with the ratio of I_2/LiI due to increased dark current in the DSSC.The increased absorption of visible light by the electrolyte,the enhanced dark current,and the reduced ionic conductivity of the electrolyte contribute to the performance variation of the corresponding solid-state DSSC with increasing I_2 concentration.
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