image: Through a broad scale from molecular, to micro-nano scale, and to macroscopic level, organic luminescent microwires of cocrystal, solid solution, and core-shell microstructures are constructed, which is a feasible approach for the multiscale synthesis of novel luminescent organic semiconductor materials. view more
Credit: ©Science China Press
White-light emission shows great potential in practical applications of lasers, full color displays, solid-state lighting sources, and the backlights of portable display devices. Organic semiconductor luminescent materials feature the designable molecular structure, tunable optoelectronic properties and easy low-temperature solution processing, which make that white light emission based on organic luminescent materials hold exotic fundamental research value and broad application prospects. In pursuit of high-performance semiconductor luminescent materials, one approach is the chemical synthesis route for new molecules. Another alternative strategy is the fine synthesis of new macroscopic structures composed of organic molecules. Organic micro-nanocrystals have the characteristic advantages of bulk single crystal materials, such as minimal defect density, the absence of grain boundaries, smooth morphologies and ordered molecular arrangement. In particular, the multifunctional organic micro-nano crystalline structure composed of different photo-functional materials exhibits excellent photophysical/chemical properties, which is of great significance to the organic light-emitting source system. However, there are still challenges in the precise synthesis of organic heterostructures, which is due to the lattice differences between multi-components and the lack of universal strategy for the accurate modulation of the dynamic self-assembly process in organic system.
Recently, Prof. Xue-Dong Wang and co-workers from the Institute of Functional Nano & Soft Materials (FUNSOM) of Soochow University selectively introduced and manipulated the weak intermolecular non-covalent interactions: charge transfer interactions in the same molecular system, demonstrating the multiscale construction of organic luminescent microwires such as cocrystals, solid solutions, and core-shell microstructures. Through the wide selection of electron donor/acceptor pairs, a series of color-tunable charge-transfer (CT) cocrystals are formed via the intermolecular cooperative self-assembly process. On this basis, the high structural compatibility and perfect lattice mismatching (»1.1%) of cocrystals are critical factors that facilitate the combination of dissimilar materials to form solid solutions and core/shell microwires. Significantly, because of the full-spectrum light transport from 400 to 800 nm, the nano-micro-scaled solid solution microwires act as microscale white-light sources [CIE (0.32, 0.36)]. Meanwhile, the macroscopic-scale core/shell organic-microwires demonstrate tunable white-light emission with CIE coordinates ranging from (0.37, 0.39) to (0.40, 0.31). Therefore, this work provides a feasible approach to the multiscale synthesis of novel luminescent organic semiconductor materials. The first author of the paper is Song Chen from Soochow University, and the corresponding author is Prof. Xue-Dong Wang.