Sci. China Mater. 2019, 62, 1013–1022. https://link.springer.com/article/10.1007/s40843-018-9404-4

The mechanochemical route is a facile and fast way and has received much attention for developing versatile advanced functional materials. Herein, we reported a mechanochemical synthesis for incorporating divalent manganese ions (Mn^II) into a two-dimensional (2D) hybrid perovskite (C₄H₉NH₃)₂PbCl₄. The mild external stimuli originating from the grinding at room temperature enabled the formation of MnII-doped 2D hybrid perovskites, and rapidly changed the luminescence characteristics. The photoluminescence analyses show that the violet and orange emissions are attributed to (C₄H₉NH₃)₂Pb_1–xMn_xCl₄ band-edge emission and the T₁→⁶A₁ transition of Mn²⁺ resulting from an efficient energy transfer process, respectively. Site preference and distribution of the doped Mn²⁺ cations on the locations of Pb²⁺ were analyzed. The formation energy calculated by the density functional theory (DFT) indicates that the Mn²⁺ ions can rapidly enter the crystal lattice due to the unique 2D crystal structure of the hybrid perovskite. Such a case of mechanochemical synthesis for the 2D hybrid perovskite motivates many novel emerging materials and the related applications.

Adv. Opt. Mater. 2019, 7(10). https://onlinelibrary.wiley.com/doi/abs/10.1002/adom.201900139

Lead-free and stable Sn halide perovskites demonstrate tremendous potential in the field of optoelectronic devices. Here, the structure and optical properties of the “defect” perovskites Cs₂SnCl_6−xBr_x are reported, as well as their use as photodetector materials. Millimeter-sized Cs₂SnCl_6−xBr_x single crystals are grown by the hydrothermal method, with the body color continuously changing from transparent to yellow and finally to dark red. Narrowband single-crystal photodetectors using Cs₂SnCl_6−xBr_x crystals are presented, which show a high detectivity of ≈2.71 × 10¹⁰ Jones, with narrowband photodetection (full-width at half-maximum ≈45 nm) and high ion diffusion barriers. Moreover, the response spectra are continuously tuned from near violet to orange depending on the variation of the bandgap of the single crystals by changing the halide compositions. The strong surface charge recombination of the excess carriers near the crystal surfaces produced by short wavelength light elucidates the narrowband photodetection behavior. This work provides a new paradigm in the design of lead-free, stable, and high-performance perovskite derivatives for optoelectronics applications.

Light Sci Appl., 8, 38 (2019). https://www.nature.com/articles/s41377-019-0148-8

Phosphor-converted white LEDs rely on combining a blue-emitting InGaN chip with yellow and red-emitting luminescent materials. The discovery of cyan-emitting (470–500 nm) phosphors is a challenge to compensate for the spectral gap and produce full-spectrum white light. Na_0.5K_0.5Li₃SiO₄:Eu²⁺ (NKLSO:Eu²⁺) phosphor was developed with impressive properties, providing cyan emission at 486 nm with a narrow full width at half maximum (FWHM) of only 20.7 nm, and good thermal stability with an integrated emission loss of only 7% at 150 °C. The ultra-narrow-band cyan emission results from the high-symmetry cation sites, leading to almost ideal cubic coordination for UCr₄C₄-type compounds. NKLSO:Eu²⁺ phosphor allows the valley between the blue and yellow emission peaks in the white LED device to be filled, and the color-rendering index can be enhanced from 86 to 95.2, suggesting great applications in full-spectrum white LEDs.