A–D–A-Type Porphyrins for Single-Component Organic Solar Cells

Two conjugated A–D–A (A = electron acceptor, D = electron donor) porphyrins 2OH–2BT–ZnPOR and 2C60–2BT–ZnPOR are designed and synthesized for single-component organic solar cells (SCOSCs). In the two molecules, two benzothiadiazoles (BTs) are connected to a porphyrin core as the electron-withdrawing units through π-bridges to build a conjugated A–D–A main chain, which can narrow the energy levels, broaden the absorption, and promote the intramolecular charge transfer of the porphyrins. While there are no other electron-acceptor side groups in 2OH–2BT–ZnPOR, two fullerene units are symmetrically connected to 2OH–2BT–ZnPOR in 2C60–2BT–ZnPOR. Though the 2OH–2BT–ZnPOR-based SCOSCs exhibit a very poor device performances, the 2C60–2BT–ZnPOR-based SCOSC shows a power conversion efficiency (PCE) of 1.51% and a high open-circuit voltage (V OC) of 1.05 V, which is also much higher than those of previously reported porphyrin-based SCOSCs. The much higher performance of 2C60–2BT–ZnPOR SCOSCs can be ascribed to the delocalized π-electrons induced by the conjugated A–D–A main chain and the promoted charge dissociation induced by the fullerene units in 2C60–2BT–ZnPOR.