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All-inorganic cesium copper halide nanocrystals have attracted extensive attention due to their cost-effectiveness, low toxicity, and rich luminescence properties. However, controlling the synthesis of these nanocrystals to achieve a precise composition and high luminous efficiency remains a challenge that limits their future application. Herein, we report the effect of oleylammonium iodide on the synthesis of copper halide nanocrystals to control the composition and phase and modulate their photoluminescence (PL) quantum yields (QYs). For CsCu 2 I 3 , the PL peak is centered at 560 nm with a PLQY of 47.3%, while the PL peak of Cs 3 Cu 2 I 5 is located at 440 nm with an unprecedently high PLQY of 95.3%. Furthermore, the intermediate-state CsCu 2 I 3 /Cs 3 Cu 2 I 5 heterostructure shows white light emission with a PLQY of 66.4%, chromaticity coordinates of (0.3176, 0.3306), a high color rendering index (CRI) of 90, and a correlated color temperature (CCT) of 6234 K, indicating that it is promising for single-component white-light-emitting applications. The nanocrystals reported in this study have excellent luminescence properties, low toxicity, and superior stability, so they are more suitable for future light-emitting applications.

Materials with two or more fluorescence features under different excitation sources have great potential in optical applications, but luminous materials with three emission characteristics have been largely undeveloped. Here, we report a novel zero-dimensional (0D) organic-inorganic hybrid ((C 2 H 5 ) 4 N) 2 ZrCl 6 perovskite with multiple emissions. The zirconium-based perovskite exhibits a red emission around 620 nm, a green emission at 527 nm, and a blue emission around 500 nm. The red and green emissions come from self-trapped excitons (STEs) and the d-d transitions of Zr(iv), respectively, which are caused by distortion of the [ZrCl 6 ] 2- octahedra. The blue emission is caused by thermally activated delayed fluorescence (TADF), which is similar to that of Cs 2 ZrCl 6 . The absolute photoluminescence quantum yield (PLQY) of the red and blue double emission is up to 83% and the PLQY of the green emission is 27%. With different combinations of ((C 2 H 5 ) 4 N) 2 ZrCl 6 samples, we achieve a variety of applications, including a two-color luminescent anti-counterfeiting device, a white light-emitting diode (WLED) with a color rendering index (CRI) of 95 and information encryption with different excitations. We also synthesize other hybrid zirconium perovskites with tri-luminescence through a similar method. Our work provides a potential set of excitation-dependent luminescent materials and is expected to expand the basic research and practical applications of multi-luminescence materials., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Recently, lead halide perovskite nanocrystals (NCs) have attracted extensive attention due to their unique optical properties. However, the toxicity of lead and the instability to moisture obstruct their further commercial development. Herein, a series of lead-free CsMnX 3 (X = Cl, Br, and I) NCs embedded in glasses were synthesized by a high temperature solid-state chemistry method. These NCs embedded in glass can remain stable after soaking in water for 90 days. It is found that increasing the amount of cesium carbonate in the synthesis process can not only prevent the oxidation of Mn 2+ to Mn 3+ and promote the transparency of glass in the 450-700 nm region, but also significantly increase its photoluminescence quantum yield (PLQY) from 2.9% to 65.1%, which is the highest reported value of the red CsMnX 3 NCs so far. Using CsMnBr 3 NCs with a red emission peak at 649 nm and full-width-at-half-maximum (FWHM) of 130 nm as the red light source, a white light-emitting diode (LED) device with International Commission on illumination (CIE) coordinates of (0.33, 0.36) and a color rendering index (CRI) of 94 was obtained. These findings, together with future research, are likely to yield stable and bright lead-free NCs for the next generation of solid-state lighting., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

The absorption and photoluminescence (PL) of CsMnBr 3 with Mn(II) in octahedral crystal fields are extremely weak due to a d-d forbidden transition. Herein, we introduce a facile and general synthetic procedure that can prepare undoped and heterometallic doped CsMnBr 3 NCs at room temperature. Importantly, both PL and absorption of CsMnBr 3 NCs were significantly improved after doping a small amount of Pb 2+ (4.9%). The absolute photoluminescence quantum yield (PL QY) of Pb-doped CsMnBr 3 NCs is up to 41.5%, 11-fold higher than undoped CsMnBr 3 NCs (3.7%). The PL enhancement is attributed to the synergistic effects between [MnBr 6 ] 4- units and [PbBr 6 ] 4- units. Furthermore, we verified the similar synergistic effects between [MnBr 6 ] 4- units and [SbBr 6 ] 4- units in Sb-doped CsMnBr 3 NCs. Our results highlight the potential of tailoring luminescence properties of manganese halides through heterometallic doping.