A new 2:1 donor (D):acceptor (A) mixed-stacked charge-transfer (CT) cocrystal comprising isometrically structured dicyanodistyrylbenzene-based D and A molecules is designed and synthesized. Uniform 2D-type morphology is manifested by the exquisite interplay of intermolecular interactions. In addition to its appealing structural features, unique optoelectronic properties are unveiled. Exceptionally high photoluminescence quantum yield (Φ ≈ 60%) is realized by non-negligible oscillator strength of the S transition, and rigidified 2D-type structure. Moreover, this luminescent 2D-type CT crystal exhibits balanced ambipolar transport (µ and µ of ≈10 cm V s ). As a consequence of such unique optoelectronic characteristics, the first CT electroluminescence is demonstrated in a single active-layered organic light-emitting transistor (OLET) device. The external quantum efficiency of this OLET is as high as 1.5% to suggest a promising potential of luminescent mixed-stacked CT cocrystals in OLET applications.

We report on a molecularly tailored 1:1 donor-acceptor (D-A) charge-transfer (CT) cocrystal that manifests strongly red-shifted CT luminescence characteristics, as well as noteworthy reconfigurable self-assembling behaviors. A loosely packed molecular organization is obtained as a consequence of the noncentrosymmetric chemical structure of molecule A1, which gives rise to considerable free volume and weak intermolecular interactions. The stacking features of the CT complex result in an external stimuli-responsive molecular stacking reorganization between the mixed and demixed phases of the D-A pair. Accordingly, high-contrast fluorescence switching (red↔blue) is realized on the basis of the strong alternation of the electronic properties between the mixed and demixed phases. A combination of structural, spectroscopic, and computational studies reveal the underlying mechanism of this stimuli-responsive behavior.

A fluorinated indolo[3,2-b]indole (IDID) derivative is prepared as a crystalline hole transporting material for perovskite solar cells. A fluorinated IDID backbone enables a tight molecular stacking by π–π interaction. The device fabricated using IDIDF exhibits a PCE of 19%.

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A new high-performing small molecule n-channel semiconductor based on diketopyrrolopyrrole (DPP), 2,2 ′ -(5,5 ′ -(2,5-bis(2-ethylhexyl)-3,6-dioxo-2,3,5,6tetrahydropyrrolo[3,4-c]pyrrole-1,4-diyl)bis(thiophene-5,2-diyl))bis(methan-1-yl-1-ylidene)dimalononitrile (DPP-T-DCV), is successfully synthesized. The frontier molecular orbitals in this designed structure are elaborately tuned by introducing a strong electron-accepting functionality (dicyanovinyl). The well-defi ned lamellar structures of the crystals display a uniform terrace step height corresponding to a molecular monolayer in the solid-state. As a result of this tuning and the remarkable crystallinity derived from the conformational planarity, organic fi eld-effect transistors (OFETs) based on densepacked solution-processed single-crystals of DPP-T-DCV exhibit an electron mobility ( μ e ) up to 0.96 cm 2 V − 1 s − 1 , one of the highest values yet obtained for DPP derivative-based n-channel OFETs. Polycrystalline OFETs show promise (with an μ e up to 0.64 cm 2 V − 1 s − 1 ) for practical utility in organic device applications.