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

• Published in: Journal of power sources 2013-11, Vol.242, p.860-864
• Main Authors: Wang, Xiao-Feng, Tamiaki, Hitoshi, Kitao, Osamu, Ikeuchi, Toshitaka, Sasaki, Shin-ichi
• Format: Article
• Language: English
• Subjects: Applied sciences; Dye adsorption; Dye-sensitized solar cells; Energy; Exact sciences and technology; Natural energy; Photosynthetic pigments; Photovoltaic conversion; Solar cells. Photoelectrochemical cells; Solar energy; Substituent effect
• ISSN: 0378-7753; 1873-2755
• DOI: 10.1016/j.jpowsour.2013.05.191

This work demonstrates a strategy to improve the photovoltaic performance of a well-known chlorophyll derivative, chlorin e6, with molecular engineering. By introducing alkyl ester substituents at the C15 and C17 positions of the chlorin macrocycle of chlorin e6, the short-circuit photocurrent (Jsc), the open-circuit photovoltage (Voc), 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 Jsc = 15.6 mA cm−2, Voc = 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 TiO2 semiconductor and redox couple in the electrolyte as well as the enhanced electron-injection and light-harvesting efficiencies. •Chlorin e6 derivatives were synthesized and used for dye-sensitized solar cells for the first time.•A high power-conversion efficiency of up to 6.7% was achieved for the best solar cell.•This study investigated the effects of both the alkyl substituents and the carboxy group's position on the chlorin macrocycles.