Scalable Synthesis of Organic Core/Shell Architectures toward Dual-Wavelength Optical Waveguides.

Organic core/shell heterostructures have undergone rapid progress in materials chemistry owing to the integration of a wide array of unique properties. Nonetheless, the intricate challenge of regulating homogeneous nucleation and phase separation processes in excessively analogous cocrystal structures presents a formidable barrier to expanding the synthesis strategy for organic core/shell heterostructures. Herein, we successfully achieved a phase separation growth process facilitated by the organic alloy interface layer through a dynamic visualization to capture the intricate morphological evolution. By finely regulating the nucleation process, homogeneous self-assembly induced by high chemical and structural compatibility is circumvented, enabling the formation of organic core/shell heterostructures. Notably, this core/shell architecture boasts dual-wavelength emission at 496 and 696 nm, accompanied by an optical loss coefficient of 0.092 dB per micrometer. This methodology shows potential for extending to the scalable design of other conformational cocrystal heterostructure systems, thereby offering valuable insights into the realm of organic photonics.

Epitaxial Growth of Two-Dimensional Organic Crystals with In-Plane Heterostructured Domain Regulation.

Complex organic lateral heterostructures (OLHs) with spatial distribution of two or more chemical components are crucial for designing and realizing unique structure-dependent optoelectronic applications. However, the precise design of well-defined OLHs with flexible domain regulation remains a considerable challenge. Herein, we present a stepwise solution self-assembly method to synthesize two-dimensional (2D) OLHs with a central rhombus domain and a lateral region featuring tunable blue and green emission based on the sequential nucleation and growth of 2D crystals. By controlling the initial crystallization time of 2,6-diphenylanthracene, the rhombic length ratio (α) of the multicolor-emissive part of the 2D OLHs is precisely modified. Furthermore, a third lateral layer is constructed on the resulting OLHs, demonstrating scalable lateral regulation. Significantly, these prepared 2D OLHs exhibit great excitation position-dependent waveguide characteristics and enable a 0.06 dB/µm low-loss waveguiding, which are conducive to photon transport and conversion for photonic integrated circuits. This work provides a stepwise strategy for the accurate fabrication of 2D OLHs, fabricating the developments of next-generation optoelectronics devices.

Customizable Organic Charge-Transfer Cocrystals for the Dual-Mode Optoelectronics in the NIR (II) Window.

Organic molecules have been regarded as ideal candidates for near-infrared (NIR) optoelectronic active materials due to their customizability and ease of large-scale production. However, constrained by the intricate molecular design and severe energy gap law, the realization of optoelectronic devices in the second near-infrared (NIR (II)) region with required narrow band gaps presents more challenges. Herein, we have originally proposed a cocrystal strategy that utilizes intermolecular charge-transfer interaction to drive the redshift of absorption and emission spectra of a series BFXTQ (X = 0, 1, 2, 4) cocrystals, resulting in the spectra located at NIR (II) window and reducing the optical bandgap to ∼0.98 eV. Significantly, these BFXTQ-based optoelectronic devices can exhibit dual-mode optoelectronic characteristics. An investigation of a series of BFXTQ-based photodetectors exhibits detectivity (D*) surpassing 1013 Jones at 375 to 1064 nm with a maximum of 1.76 × 1014 Jones at 1064 nm. Moreover, the radiative transition of CT excitons within the cocrystals triggers NIR emission over 1000 nm with a photoluminescence quantum yield (PLQY) of ∼4.6% as well as optical waveguide behavior with a low optical-loss coefficient of 0.0097 dB/µm at 950 nm. These results promote the advancement of an emerging cocrystal approach in micro/nanoscale NIR multifunctional optoelectronics.

Organic Cocrystal Alloys: From Three Primary Colors to Continuously Tunable Emission and Applications on Optical Waveguides and Displays.

Multicolor luminescence of organic fluorescent materials is an essential part of lighting and optical communication. However, the conventional construction of a multicolor luminescence system based on integrating multiple organic fluorescent materials of a single emission band remains complicated and to be improved. Herein, organic alloys (OAs) capable of full-color emission are synthesized based on charge transfer (CT) cocrystals. By adjusting the molar ratio of electron donors, the emission color of the OAs can be conveniently and continuously regulated in a wide visible range from blue (CIE: 0.187, 0.277), to green (CIE: 0.301, 0.550), and to red (CIE: 0.561, 0.435). The OAs show analogous 1D morphology with smooth surface, allowing for full-color waveguides with low optical-loss coefficient. Impressively, full-color optical displays are easily achieved through the OAs system with continuous emission, which shows promising applications in the field of optical display and promotes the development of organic photonics.