Abstract
Extending photoresponse ranges of semiconductors to the entire ultraviolet–visible (UV)–shortwave near-infrared (SWIR) region (ca. 200–3000 nm) is highly desirable to reduce complexity and cost of photodetectors or to promote power conversion efficiency of solar cells. The observed up limit of photoresponse for organic-based semiconductors is about 1800 nm, far from covering the UV–SWIR region. Here we develop a cyanide-bridged layer-directed intercalation approach and obtain a series of two viologen-based 2D semiconductors with multispectral photoresponse. In these compounds, infinitely π-stacked redox-active N-methyl bipyridinium cations with near-planar structures are sandwiched by cyanide-bridged MnII–FeIII or ZnII–FeIII layers. Radical–π interactions among the infinitely π-stacked N-methyl bipyridinium components favor the extension of absorption range. Both semiconductors show light/thermo-induced color change with the formation of stable radicals. They have intrinsic photocurrent response in the range of at least 355–2400 nm, which exceeds all reported values for known single-component organic-based semiconductors.
Highlights
Extending photoresponse ranges of semiconductors to the entire ultraviolet–visible (UV)–shortwave near-infrared (SWIR) region is highly desirable to reduce complexity and cost of photodetectors or to promote power conversion efficiency of solar cells
Photoresponse range is a metric that significantly affects the potentials of semiconductors for photodetection, solar energy conversion and other applications[1,2,3,4]
Strong cation···π interactions between viologen components favor the construction of organic semiconductors, and conductance and photoconductance of viologen-based semiconductors may dramatically increase after photoinduced electron transfer (PET) and generation of free radical products[19,20,21]
Summary
Extending photoresponse ranges of semiconductors to the entire ultraviolet–visible (UV)–shortwave near-infrared (SWIR) region (ca. 200–3000 nm) is highly desirable to reduce complexity and cost of photodetectors or to promote power conversion efficiency of solar cells. We develop a cyanide-bridged layer-directed intercalation approach and obtain a series of two viologen-based 2D semiconductors with multispectral photoresponse In these compounds, infinitely π-stacked redox-active N-methyl bipyridinium cations with near-planar structures are sandwiched by cyanide-bridged MnII–FeIII or ZnII–FeIII layers. Radical–π interactions among the infinitely πstacked N-methyl bipyridinium components favor the extension of absorption range Both semiconductors show light/thermo-induced color change with the formation of stable radicals. The above issues for both photodetection and solar energy conversion devices are promisingly avoided, if a single semiconductor material with a photoresponsive range covering the entire UV–SWIR region is applied[10,12]. It is still of importance to develop effective and general design methods for single-component organic-based semiconductors with intrinsic photoresponse in the entire UV–SWIR range. Several examples have demonstrated that, the stability of viologen radicals can be clearly improved when the radicals are loaded in a porous framework[31,32] or sandwiched by inorganic layers[33] to avoid contact with oxygen
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