By now, it remains a big challenge for the development of molecules for chiral organic semiconductors, because principles for design of chiral chromophores with highly-efficient and selective circularly polarized light (CPL) absorptions (e.g., designing highly distorted π-systems) have always been contradicted with the requirements for better charge transport abilities (e.g., extended planar π-system).
In this manuscript, we introduce a skeleton merging approach to address the dilemma during the development of chiral organic semiconductors. Regioselective ortho-π-extention of a perylene diimide (PDI) core with four fused heteroaromatics leads to the formation a special PDI double-heterohelicene, which both inherits a high dissymmetry factor from the helicene skeleton and maintains an outstanding charge transport ability from the extended PDI skeleton. This reconciliation between chiroptical and electronic characteristics in one PDI double-heterohelicene structure represents a big step forward in the development of chiral organic semiconductors.
Besides these two indispensable characteristics, the fusion of tetra-indole to PDI ring brings about near-infrared light (NIR) absorption and ambipolar charge transport properties, endowing the organic phototransistors with high photoresponsivity (R) and specific detectivity (D*), along with a high external quantum efficiency under NIR light irradiations.
With multiple excellent characteristics, the corresponding organic phototransistor exhibits highest external quantum efficiency among thin film based organic CPL detectors reported to date. Especially, its photoresponsivity is even superior to the reported chiral NIR light detectors based on silicon and chiral plasmonic patterned electrodes. Finally, the ortho-π-extended PDI double-heterohelicene allows CPL detection using chiral organic semiconductors at NIR spectral region for the first time, together with excellent thermal stability. This will provide unprecedented opportunities in optoelectronics by introducing new polarization functionality to various applications.
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