A new BODIPY dimer containing carbazole group as a small molecule donor for ternary organic solar cells with the PCE up to 14.97%

The investigation of donor based on small molecules as the active component of bulk-heterojunction organic solar cells (BHJ-OSCs) continues to attract great attention due to their advantages over polymer solar cells. Herein, we report the synthesis and solar cell fabrication of small molecule donors based on BODIPY dimer. The BODIPY dimer features thiophene and carbazole groups as donor units attached to the alpha and beta-positions of the BODIPY core and dicyanodistyryl group as bridging group, and which is named as DI-BDP-CZ and showing complementary absorption with PC71BM and Y6. The electrochemical research results indicate that the frontier energy levels of DI-BDP-CZ (HOMO = -5.55 eV and LUMO = -3.83 eV) is well matched with energy levels of both PC71BM and Y6. The photovoltaic performance of DI-BDP-CZ used as electron-donors along with PC71BM or Y6 as acceptor was evaluated in bulk heterojunction organic solar cells. The OSCs based on optimized DI-BDPCZ: PC71BM and DI-BDP-CZ: Y6 attained overall PCE of 7.63% and 12.58%, respectively. After the optimization of the active layer, the ternary organic solar cells based on DI-BDP-CZ: PC71BM:Y6 can achieve overall power conversion efficiency (PCE) as high as 14.97%, which is higher than the corresponding binary organic solar cells. The higher PCE of the ternary OSC is ascribed to the efficient exciton dissociation, balanced charge transport, better crystallinity and appropriate phase separation.

Automated summary

In this study, we synthesized and fabricated small molecule donors based on BODIPY dimer, named DI-BDP-CZ, for organic solar cells. The electrochemical research demonstrated that DI-BDP-CZ had energy levels well matched with both PC71BM and Y6. The optimized DI-BDPCZ: PC71BM and DI-BDP-CZ: Y6 based organic solar cells achieved overall power conversion efficiency of 7.63% and 12.58%, respectively.