In order to achieve a high quantum efficiency, doping crystals with appropriate elements such as sodium cations (ref. [8]) to reduce electronic dimension is a useful method. [5,8] However, doping also tends to cause nonradiation recombination loss. [13] Therefore, a reliable and promising way is to synthesize high-quality inorganic metal halide single crystal (SC) with natural lowdimensional structure to realize stable and high quantum efficiency white-light illumination application.In this work, we successfully synthesized 1D CsCu 2 I 3 SC by replacing toxic Pb with eco-friendly and abundant Cu, and organic molecules with large-radius Cs. [12,13] The "one dimension" we noted here is localized dimension of electron. [14] Through density functional theory (DFT) calculation, in 1D CsCu 2 I 3 SC, [Cu 2 I 3 ] − octahedra contributes most electronic states, and Cs + only forms a 1D electronic structure with isolated [Cu 2 I 3 ] − in 2D direction. Therefore, CsCu 2 I 3 SC obtains a high photoluminescence quantum yield (PLQY ≈15.7%) of the IWE at room temperature. [2] We also calculated that the crystal has a high radiation recombination rate which is owning to the 1D localized electronic structure, and this rate is the key to its high PLQY. [15,16] Under a strong injection and atmospheric environment, the PL intensity of all-inorganic CsCu 2 I 3 SC only decays about 5% after 750 min ( Figure S5, Supporting Information). This excellent stability demonstrates that the all-inorganic CsCu 2 I 3 SC possesses a great prospect in high-efficiency lighting applications.High-quality CsCu 2 I 3 SCs were synthesized by antisolvent infiltration method. [17,18] Cesium iodide and cuprous (I) iodide in certain ratio were dissolved in dimethyl formamide (DMF)dimethyl sulfoxide (DMSO) (4:1) to obtain a saturated solution. Then, methanol (antisolvent) was slowly dropped into the saturated solution to form a white precipitate (the white precipitate quickly dissolved again) until it no longer dissolved. The solution was filtered and then placed in a beaker with methanol atmosphere to grow crystals. Several days later, centimeter-scale high-quality CsCu 2 I 3 SCs were obtained (refer to the Supporting information and the Experimental Section for more details). Figure 1a shows an optical image of a rod-shaped CsCu 2 I 3 SCs excited by ultraviolet light. The SC has a size of about 10 mm × 1.5 mm, being colorless and transparent at room temperature but having strong white-light emission under ultraviolet light. Crystal structure of the CsCu 2 I 3 SC was obtained through single-crystal X-ray diffraction (SCXRD) test (Figure 1b,c), which belongs to orthorhombic system. The 1D Energy-saving white lighting from the efficient intrinsic emission of semiconductors is considered as a next-generation lighting source. Currently, white-light emission can be composited with a blue light-emitting diode and yellow phosphor. However, this solution has an inevitable light loss, which makes the improvement of the energy utilization efficiency more difficult. T...

Low-dimensional metal halide perovskites possessing a large exciton binding energy have shown great promise in achieving efficient photonic emission required in the fields of lighting sources and display. Here, efficient dual self-trapped exciton (STE) emissions are directly observed in a low-dimensional inorganic copper iodine quasiperovskite single crystal. The dual STEs have natural structure-oriented performance, showing a strong electron−phonon coupling. Temperaturedependent PL spectra and Raman spectra demonstrate a thermal-assisted radiative recombination of dark STEs, and based on such a mechanism, an ultrahigh photoluminescence quantum yield (PLQY∼100%) was obtained in bulk crystals with a zero-dimensional electronic structure, favoring photoexcited STEs to gain a large binding energy of up to 563 meV. All these results above show a great advancement in high-efficiency photonic emission through the low-dimensional electronic structure and STE radiative recombination.

The precise precursor supply is a precondition for controllable growth of two-dimensional (2D) transition metal dichalcogenides (TMDs). Although great efforts have been devoted to modulating the transition metal supply, few effective methods of chalcogen feeding control were developed. Here we report a strategy of using active chalcogen monomer supply to grow high-quality TMDs in a robust and controllable manner, e.g., MoS2 monolayers perform representative photoluminescent circular helicity of ~92% and electronic mobility of ~42 cm2V−1s−1. Meanwhile, a uniform quaternary TMD alloy with three different anions, i.e., MoS2(1-x-y)Se2xTe2y, was accomplished. Our mechanism study revealed that the active chalcogen monomers can bind and diffuse freely on a TMD surface, which enables the effective nucleation, reaction, vacancy healing and alloy formation during the growth. Our work offers a degree of freedom for the controllable synthesis of 2D compounds and their alloys, benefiting the development of high-end devices with desired 2D materials.

No abstract

No abstract