Demonstration of a Broadband Photodetector Based on a Two-Dimensional Metal-Organic Framework

Metal-organic frameworks (MOFs) are emerging as an appealing class of highly tailorable electrically conducting materials with potential applications in optoelectronics. Yet, the realization of their proof-of-concept devices remains a daunting challenge, attributed to their poor electrical properties. Following recent work on a semiconducting Fe₃ (THT)₂ (NH₄ )₃ (THT: 2,3,6,7,10,11-triphenylenehexathiol) 2D MOF with record-high mobility and band-like charge transport, here, an Fe₃ (THT)₂ (NH₄ )₃ MOF-based photodetector operating in photoconductive mode capable of detecting a broad wavelength range from UV to NIR (400-1575 nm) is demonstrated. The narrow IR bandgap of the active layer (≈0.45 eV) constrains the performance of the photodetector at room temperature by band-to-band thermal excitation of charge carriers. At 77 K, the device performance is significantly improved; two orders of magnitude higher voltage responsivity, lower noise equivalent power, and higher specific detectivity of 7 × 10⁸ cm Hz^1/2 W^-1 are achieved under 785 nm excitation. These figures of merit are retained over the analyzed spectral region (400-1575 nm) and are commensurate to those obtained with the first demonstrations of graphene- and black-phosphorus-based photodetectors. This work demonstrates the feasibility of integrating conjugated MOFs as an active element into broadband photodetectors, thus bridging the gap between materials' synthesis and technological applications.