Cocrystal Engineering: Toward Solution‐Processed Near‐Infrared 2D Organic Cocrystals for Broadband Photodetection

Abstract Large‐area 2D cocrystals with strong near‐infrared (NIR) absorption have been designed and prepared. Driven by the intermolecular charge‐transfer (CT) interactions, zinc tetraphenylporphyrin (donor) and C 60 (acceptor) self‐assemble into a NIR cocrystal with absorption wavelength up to 1080 nm. By tailoring the growth solvents and processes, the cocrystal morphologies can be tuned from 1D nanowires, 2D nanosheets to large‐area 2D cocrystal films with length reaching several millimeters. Owing to the highly ordered donor–acceptor arrangement, the CT absorption in the 2D cocrystals is enhanced and is comparable to singlet absorption. The uniform 2D cocrystals, with enhanced CT absorption in the NIR region, displays a high responsivity of 2424 mA W −1 to NIR light and a fast response time of 0.6 s. The excellent device performance is attributed to the generation of long‐lived free charge carriers as revealed by transient absorption spectroscopy and optimization of device configuration.