Nanographene-Based Metal-Organic Framework Thin Films: Optimized Packing and Efficient Electron-Hole Separation Yielding Efficient Photodetector

Organic semiconductors, specifically polycyclic aromatic chromophores like pentacene, coronene, and nanographenes (hexa-peri-hexabenzocoronene, HBC), are often utilized in optoelectronic applications due to their intriguing single-molecule properties. However, the integration of these aromatic compounds into optoelectronic devices frequently encounters significant obstacles, primarily due to the unpredictable and challenging control over the structure and morphology of their condensed phase. Rather than resorting to chemical modifications or advanced thin-film manufacturing methods such as chemical vapor deposition, the so-called metal-organic framework (MOF) approach is employed to create a highly photoresponsive, nanographene-based thin film employing a layer-by-layer, liquid-phase epitaxy method. It is demonstrated that the novel Cu-HBC MOF thin film exhibits excellent photoresponsive behavior under ultraviolet illumination, including a fast response time (< 0.02 s) and high current switching ratio (approximate to 104), which significantly outperforms an isostructural MOF Zn-HBC. Furthermore, it is demonstrated that the metal nodes inside the MOF can be used to enhance the photoresponse by efficient exciton splitting. Novel hexa-peri-hexabenzocoronene (HBC) chromophore-based metal-organic framework (MOF) thin films are synthesized by using a layer-by-layer synthesis method. Cu-HBC thin film exhibits excellent photoresponsive behavior under ultraviolet illumination, including a high switching ratio (approximate to 104) and fast response time (< 20 ms), significantly outperforming an isostructural MOF Zn-HBC. This high performance is attributed to the photo-induced ligand-to-metal charge transfer process between HBC and Cu2+.image