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 J_sc = 11.46 mA/cm², V_oc = 0.90 V, and FF = 0.61. A remarkable value of incident photon-to-current conversion efficiency (IPCE) of 61% has also been observed.