Alkyloxy substituted organic dyes for high voltage dye-sensitized solar cell: Effect of alkyloxy chain length on open-circuit voltage

Three novel organic dyes (SB1, SB2, and SB3) containing 4-(hexyloxy)-N-(4-(hexyloxy)phenyl)-N-phenylaniline as electron donor and cyanoacrylic acid as electron acceptor bridged by alkyloxy (methyl = SB1, propyl = SB2 and hexyl = SB3) substituted p-phenylenevinylene linkers have been synthesized. Density functional theory (DFT) has employed to study electron distribution and intramolecular charge transfer. Increase in alkyl chain length in alkyloxy substituent leads to increase in open-circuit voltage (VOC), which is found to be related to the increased electron lifetime at open-circuit condition. Under AM 1.5 G 1 sun light illumination (100 mW/cm2), an optimized SB3-sensitized cell show a short-circuit photocurrent density (JSC) of 12.83 mA/cm2, an open-circuit voltage (VOC) of 0.745 V and a fill factor (FF) of 0.64, corresponding to an overall conversion efficiency (η) of 6.12%. Little degradation in η observed over 40 days is indicative of long-term stability of the SB-series dyes.

► Organic dyes with different alkyloxy chain length were synthesized.
► Increase in alkyl chain length in alkyloxy substituent increases open-circuit voltage.
► Long alkyloxy chain retarded recombination rate.