Theoretical Design of D−π–A–A Sensitizers with Narrow Band Gap and Broad Spectral Response Based on Boron Dipyrromethene for Dye-Sensitized Solar Cells

Dye-sensitized solar cells based on boron dipyrromethene (BODIPY) have gained widespread attention in recent years because of their easy structural modification, strong light absorption, and photostability. In this paper, a series of dyes with single or double acceptors based on the BODIPY framework have been designed and compared by density functional theory calculation. Results show that the dyes with double acceptors exhibit smaller band gap and broader red-shift absorption peaks than their counterparts with single acceptors. To further improve the dye performance, polythiophenes and electron donating groups are successively introduced into BODIPY and donor moieties of double-acceptor dyes. The introduction of polythiophene effectively improved the light harvesting efficiency (LHE) from 0.79 to 0.96. And, the stronger electron donating groups create a narrow band gap, resulting in a broad absorption band in the range of 400–1600 nm. These modifications not only broaden the absorption range but also facilitate electron injection, thereby improving the photoelectric conversion efficiency, which is beneficial for the potential application of BODIPY sensitizers in the field of photovoltaics.