The impact of an indeno[1,2-b]thiophene spacer on dye-sensitized solar cell performances of cyclic thiourea functionalized organic sensitizers

Two new organic sensitizers (JK-313 and JK-314) possessing bulky cyclic thiourea functionalized triphenylamine as an electron donor were designed and synthesized. Especially, JK-314 showed a strong molar absorption coefficient and a red-shifted absorption compared with JK-313 due to its planar indeno[1,2-b]thiophene spacer. An indeno[1,2-b]thiophene spacer as well as bulky groups on the cyclic thiourea plays a key role in preventing both the intermolecular aggregation and undesired charge recombination in DSSCs, which resulted in an improvement in both short-circuit photocurrent density (Jsc) and open-circuit voltage (Voc). Under standard AM 1.5G solar conditions, JK-314 based DSSCs in the presence of polymer gel electrolytes showed an overall power conversion efficiency (PCE) of 8.44%. It is one of the highest values in organic dye based DSSCs ever reported.