D-A-D type small molecule donors based on BODIPY skeleton for bulk heterojunction organic solar cells

Abstract

In recent years, structural modification for boron-dipyrromethene (BODIPY) derivatives has been proven to be an effective way to improve their performance of organic solar cells (OSCs). Here, three D-A-D type small molecule donors BDP-1, BDP-2 and BDP-3 were synthesized based on 3,5,8-trimethyl BODIPY dye as the core by the introduction of 4-(diethylamino)phenyl, 4-diethylamino-2-methoxyphenyl and 4-(diphenylamino)phenyl at the 3, 5 and 8 positions, respectively, and used for the construction of organic solar cells. BDP-1, BDP-2, and BDP-3 are synthesized. Due to the strong electron-donating ability of the substituted groups at 3, 5, and 8 positions of BODIPY core, three donors exhibit extended π-conjugation and effective intramolecular charge transfer, resulting in the strong absorption in the range of 500–––900 nm with narrow band gaps below 1.52 eV. BDP-1, BDP-2 and BDP-3 display complementary absorption spectra and suitable highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital levels (LUMO) with fullerene derivative PC71BM. These molecules (BDP-1, BDP-2 or BDP-3) as electron donor were applied into BHJ solar cells by using PC71BM as electron acceptor. The performance of BHJ organic solar cells is systematically investigated and compared. The optimized solar cells based on BDP-1, BDP-2 and BDP-3 show high power conversion efficiencies (PCEs) of 9.52%, 11.83% and 5.27%, respectively. The OSCs based on BDP-2: PC71BM exhibited excellent short-circuit current density (Jsc), high electron mobility and open-circuit voltage (Voc). This work demonstrates that BODIPY derivatives with simple-structured show great potential for high performance OSCs.