A-D-A Type Small Molecules Based on Boron Dipyrromethene for Solution-Processed Organic Solar Cells

The unique properties of boron dipyrromethene (BODIPY) dyes including facile synthesis, high absorption coefficients, and delocalized molecular orbitals as well as excellent photochemical and thermal stability, make them promising as materials for organic solar cells. Accordingly, in this study three A-D-A structural small molecules of BDTT-BODIPY, FL-BODIPY, and TT-BODIPY have been synthesized, in which two BODIPY acceptor units are symmetrically conjugated to 4,8-bis(5-(2-ethylhexyl) thiophen-2-yl)benzo[1,2-b:4,5-b]dithiophene (BDTT), 9,9-dioctyl-9H-fluorene (FL), and thieno[3,2-b]thiophene (TT) donor cores, respectively. The manipulation of the structural parameters significantly improves the performances of the BHJ OSCs, which show power conversion efficiencies of 4.75%, 1.51%, and 1.67% based on [6,6]-phenyl C71 -butyric acid methyl ester (PC71 BM) as the acceptor material and BDTT-BODIPY, FL-BODIPY, and TT-BODIPY as the donor materials, respectively.