2D Metal–Organic Framework Cu₃(HHTT)₂ Films for Broadband Photodetectors from Ultraviolet to Mid-Infrared

Cu₃(HHTT)₂ (HHTT: 2,3,7,8,12,13-hexahydroxytetraazanaphthotetraphene) is a novel 2D conjugated metal–organic framework (2D c-MOF) with efficient in-plane d–π conjugations and strong interlayer π–π interactions while the growth of Cu₃(HHTT)₂ thin films has never been reported until now. Here, the successful fabrication of highly oriented wafer-scale Cu₃(HHTT)₂ thin films with a layer-by-layer growth method on various substrates is presented. Its semiconducting behavior and carrier transport mechanisms are clarified through temperature and frequency-dependent conductivity measurements. Flexible photodetectors based on Cu₃(HHTT)₂ thin films exhibit reliable photoresponses at room temperature in a wavelength region from UV to mid-IR, which is much broader than those of solution-processed broadband photodetectors reported previously. Moreover, the photodetectors can show a typical synaptic behavior and excellent data recognition accuracy in artificial neural networks. This work opens a window for the exploration of high-performance and multifunctional optoelectronic devices based on 2D c-MOFs.