Corrole-BODIPY Dyad as Small-Molecule Donor for Bulk Heterojunction Solar Cells

Dyes based on charge-transfer (CT) characteristics are attractive candidates for organic photovoltaics due to their intense and broad absorption window. In these molecular frameworks, electron-rich donors and electron-deficient acceptors are covalently linked to achieve an effective CT process. Corrole, a tetrapyrrolic congener of porphyrin, is an excellent example of an electron-rich molecule with a large molar extinction coefficient. BODIPY, on the other hand, is a well-known electron-deficient bypyrrolic boron difluoride complex with intense absorption complementary to the corrole. A combination of these two structural motifs should result in a dyad having a wide absorption window, which will be suitable for organic photovoltaics. Herein, a corrole derivative has been envisaged as an efficient donor for solution-processed bulk heterojunction solar cells with PC71BM as an acceptor for the first time. The current molecule exhibits broad absorption in the visible range in solution as well as in thin films, with a high molar extinction coefficient and a low band gap of 1.79 eV. Frontier molecular orbital energy levels were found to be complementary to those of the well-known acceptor PC71BM. The optimized devices based on Cor-BODIPY:PC71BM showed a high power conversion efficiency (PCE) of 6.6% with Jsc = 11.46 mA/cm2, Voc = 0.90 V, and FF = 0.61. A remarkable value of incident photon-to-current conversion efficiency (IPCE) of 61% has also been observed.