Subphthalocyanine‐Diketopyrrolopyrrole Conjugates: 3D Star‐Shaped Systems as Non‐Fullerene Acceptors in Polymer Solar Cells with High Open‐Circuit Voltage

Four star‐shaped electron acceptors (C1‐OPh, C3‐OPh, C1‐Cl and C3‐Cl) based on a subphthalocyanine core bearing three diketopyrrolopyrrole wings linked by an acetylene bridge have been synthesized. These derivatives feature two different axial substituents (i. e., 4‐tert‐butylphenoxy (OPh) or chlorine (Cl)) and for each of them, both the C1 and the C3 regioisomers have been investigated. The four compounds exhibit a broad absorption band in the 450–700 nm region, with bandgap values near to 2 eV. These materials were applied in the active layer of inverted bulk‐heterojunction polymer solar cells in combination with the donor polymer PBDB‐T. Derivatives bearing the OPh axial group showed the best performances, with C1‐OPh being the most promising with a PCE of 3.27 % and a Voc as high as 1.17 V. Despite presenting the widest absorption range, the photovoltaic results obtained with C1‐Cl turned out to be the lowest (PCE=1.01 %). Four electron acceptors comprising a subphthalocyanine core bearing three diketopyrrolopyrrole wings linked by an acetylene bridge have been synthesized. These derivatives feature tert‐butylphenoxy and chlorine as axial substituents and for each of them, both the C1 and the C3 regioisomers have been prepared. These materials were applied in the active layer of inverted bulk‐heterojunction polymer solar cells in combination with the donor polymer PBDB‐T. C1‐SubPc‐DPP‐OPh (see figure) showed the best performances with a PCE of 3.27 %.