A Strategy for Enhancing the Performance of Borondipyrromethene Dye-Sensitized Solar Cells

Borondipyrromethene (BODIPY) dyes are one of the most interesting organic dyes because of their unique characteristic in capturing near-infrared (NIR) solar radiation. However, the highest reported conversion efficiency of BODIPY dyes is still far behind that of other organic dyes. Herein, we demonstrated an efficient strategy for enhancing the photovoltaic performance of BODIPY dyes, i.e., introducing a long linker between the light harvesting antenna and acceptor. Interestingly, the linker length has opposite effects on the BODIPY (M62, M63, M66, and LB1) and triphenylamine (M64 and M65) dyes. This work suggests that the incorporated long linker in BODIPY dyes shows several favorable characteristics: (i) improving the light harvesting capability of BODIPY dyes in longer wavelength without a big change of the HOMO levels; (ii) efficiently increasing the photocurrent and photovoltage, leading to dramatically improved performance; (iii) significantly reducing the charge recombination between electrons in TiO2 and electrolyte acceptor species and oxidized dye molecules at the interface. As a result, M63 with a binary linker display a 4.79 times higher conversion efficiency compared to that of M62 with a single linker. This finding could contribute to molecular engineering in the design of highly efficient BODIPY dyes.