Spectrally Switchable Photodetection with Near-Infrared-Absorbing Covalent Organic Frameworks

Abstract

Most covalent organic frameworks (COFs) to date are made from relatively small aromatic subunits, which can only absorb the high-energy part of the visible spectrum. We have developed near-infrared-absorbing low bandgap COFs by incorporating donor-acceptor-type isoindigo- and thienoisoindigo-based building blocks. The new materials are intensely colored solids with a high degree of long-range order and a pseudo-quadratic pore geometry. Growing the COF as a vertically oriented thin film allows for the construction of an ordered interdigitated heterojunction through infiltration with a complementary semiconductor. Applying a thienoisoindigo-COF:fullerene heterojunction as the photoactive component, we realized the first COF-based UV- to NIR-responsive photodetector. We found that the spectral response of the device is reversibly switchable between blue- and red-sensitive, and green- and NIR-responsive. To the best of our knowledge, this is the first time that such nearly complete inversion of spectral sensitivity of a photodetector has been achieved. This effect could lead to potential applications in information technology or spectral imaging.

Construction of Large‐Area Ultrathin Conductive Metal–Organic Framework Films through Vapor‐Induced Conversion

“…in-plane conjugation. [5,8] However, MOFs as a class of new and popular material assembled by metals and organic ligands are widely studied and employed in various fields, due to combining advantages of both inorganic and organic matters. [9][10][11][12] Although MOFs are generally regarded as insulator, great progress on the design and construction of 2D conductive MOFs has made breakthroughs recently.…”

“…[6,13,14,[17][18][19][20] Nevertheless, some of the traditional but practical devices (e.g., field effect transistor (FET), light emitting diode (LED), light emitting transistor (LET), and so on) based on MOGA still remain at a very naive stage with almost no report. [1][2][3][4][5] The key technology about fabrication of large-area films with controllable thickness and orientation suppresses the development of devices, so the study on construction strategy is becoming extremely urgent. [21] While the opportunities to fabricate MOGA films have been explored in a few cases to date, there are still a lot of challenges to overcome: thin film quality, growth mechanism, controlling the defects, improving the stability, enhancing the electrical conductivity, and effectively manipulating charge carrier.…”

“…Owing to the novel electronic, optical, and mechanical properties, 2D materials, including organic single crystals (OSCs), graphene, graphene derivatives, perovskites, transition metal chalcogenides (TMDCs), covalent-organic frameworks (COFs), and metal-organic frameworks (MOFs), play important roles in device applications. [1][2][3][4][5][6][7] The OSCs, graphene derivatives, perovskites and TMDCs have been researched a lot in constructing devices and charge transfer mechanism. [1][2][3][4] Exhilaratingly, conductive COFs and MOFs as active materials are just starting to play important roles in electronic devices.…”

“…Exhilaratingly, conductive COFs and MOFs as active materials are just starting to play important roles in electronic devices. In spite of easy fabrication in a “top‐down” approach and rational modification, the functional groups of COFs connect building blocks, but restrain in‐plane conjugation . However, MOFs as a class of new and popular material assembled by metals and organic ligands are widely studied and employed in various fields, due to combining advantages of both inorganic and organic matters .…”

Ultrahigh Responsivity Photodetectors of 2D Covalent Organic Frameworks Integrated on Graphene

“…[28] Such high crystallinity and stacking alignment endow 2D-COF ordered π-electronic systems with the ability for charge carrier transport, implying that 2D-COFs have potential for optoelectronic applications. [29][30][31][32][33][34][35][36][37][38][39] Therefore, the optoelectronic properties of 2D-COFs are promising for programming by selecting suitable monomer combinations among abundant 2D π-electronic building blocks.Herein, we designed and synthesized certain 2D-COFs by selecting suitable tetraphenylethylene (TPE) monomers with photoelectric activities. This structure design endows 2D-COFs 2D materials exhibit superior properties in electronic and optoelectronic fields.…”