Molecular engineering on a chlorophyll derivative, chlorin e6, for significantly improved power conversion efficiency in dye-sensitized solar cells

Abstract This work demonstrates a strategy to improve the photovoltaic performance of a well-known chlorophyll derivative, chlorin e 6 , with molecular engineering. By introducing alkyl ester substituents at the C15 and C17 positions of the chlorin macrocycle of chlorin e 6 , the short-circuit photocurrent ( J sc ), the open-circuit photovoltage ( V oc ), and the solar energy-to-electricity conversion efficiency ( η ) of dye-sensitized solar cells were improved from 2.5 mA cm −2 , 0.47 V, and 0.9% to 6.6 mA cm −2 , 0.60 V, and 2.9%, respectively. The η value was further improved to 6.7% with J sc  = 15.6 mA cm −2 , V oc  = 0.65 V, and fill factor (FF) = 0.66 with relocation of the carboxy group and extension of the cyclic π system on the C3-substituent. These improvements were attributed to the reduced charge recombination between the TiO 2 semiconductor and redox couple in the electrolyte as well as the enhanced electron-injection and light-harvesting efficiencies.