Dimeric Porphyrin Small Molecules for Efficient Organic Solar Cells with High Photoelectron Response in the Near-Infrared Region

Small molecules (SMs) with elongated backbones are promising for achieving a higher photovoltaic performance. Herein, a dimeric porphyrin small molecule, ZnP2-DPP, consisting of two porphyrin units linked with an ethynylene as the core and two diketopyrrolopyrrole (DPP) units as the arms is designed and synthesized as an electron donor for solution-processed bulk-heterojunction (BHJ) organic solar cells (OSCs). A significantly enhanced power conversion efficiency of 8.45% with an impressive short-circuit current density ( J sc ) up to 19.65 mA cm –2 is achieved for the BHJ OSCs based on ZnP2-DP P under AM 1.5G irradiation (100 mW cm –2 ) compared to that for the OSCs based on the dimeric porphyrin linked with bis-ethynylenes reported previously. Furthermore, the devices show broad photoelectron responses up to 1000 nm with high near-infrared external quantum efficiency up to 66% at 780 nm. This is the first study reporting SM OSCs displaying such a large J sc of about 20 mA cm –2 simultaneously with a considerably high and deep photoelectron response of up to 1000 nm.