Facilitated Interfacial Electronic Processes By The Pi-Pi Stacked Edge-On Tetrabenzoporphyrin/Graphene Layer Enables Broadband Ultrasensitive Photodetecting With Prompt Response

Developing efficient organic photodetectors and revealing the crucial factor affecting photodetection performances are of importance in varied applications and fundamental researches. In this work, 5,15-bisdodecyl-tetrabenzoporphyrin (C12TBP)/graphene (Gr) phototransistors were fabricated through in situ retro-Diels-Alder reaction (as-formed), which demonstrates ultrahigh responsivity and specific detectivity, fast response, and broad-band detecting abilities covering UV to near-IR radiations. The interfacial and bulk layers of C12TBP films, defined as the adlayer on Gr sheet and the other part of the films, respectively, were characterized in detail. The pi-pi stacked edge-on C12TBP/Gr interfacial layer is suggested as the key factor enabling the ultrasensitive photodetection through facilitating the multistep interfacial electronic processes for photocurrent generation. Frontier molecular orbitals overlap effectively in the neighbor pi-pi stacked C12TBP, which promotes not only the diffusion of photogenerated electron-hole pairs but also dissociation of electron-hole pairs and charge-transfer (CT) state through weakening the electron-hole binding by dispersing charges within C12TBP columns. The separation of CT state is boosted by the large distance between the holes in Gr and the electrons in the edge-on orientation of C12TBP as well. In addition, we found that the structural evolution of the interfacial layer has a significant difference from that of the bulk layers because of the strong adsorption to the substrate. The results provide valuable support for understanding the complicated relationship between the structures and electronic properties of interfacial layers and pave the way for fabricating high-performance organic photodetecting devices.