Ratiometric optical thermometer based on the use of manganese(II)-doped Cs3Cu2I5 thermochromic and fluorescent halides

Ultrasound-assisted nucleation and growth of hydroxyl-protected and ligand-free Cs3Cu2X5 nanocrystals with bright luminescence

The commercial applications of lead halide perovskites are hindered by their negative environmental impact and inherent instability. Consequently, developing environmentally friendly copper-based perovskite materials is crucial for future solid-state lighting and display applications. In this study, an ultrafast high-power ultrasonic synthesis strategy was utilized to achieve uniform nucleation and growth of Cs3Cu2X5 (X = Cl, Br, I) nanocrystals (NCs) that possess remarkable luminescence properties, hydroxyl protection, and ligand-free characteristics. These Cs3Cu2X5 NCs exhibited a tunable spectral range spanning from 446 to 525 nm, accompanied by photoluminescence quantum yields (PLQYs) varying from 0.2% to 79.2%. The spectral attributes of the NCs were effectively controlled by modulating the halide type and composition. It is worth noting that density functional theory (DFT) calculations offer valuable insights into the synthesis of NCs and the selection of suitable alcohol solvents. Moreover, we successfully fabricated an efficient and stable white light-emitting diode (WLED) with a high luminous efficiency of 23 lm W-1 and CIE color coordinates of (0.3266, 0.3487). Our work provides a new strategy to synthesize Cs3Cu2X5 NCs and holds promise for their potential application in display and lighting devices.

Alkylammonium Halides for Phase Regulation and Luminescence Modulation of Cesium Copper Iodide Nanocrystals for Light-Emitting Diodes

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 CsCu2I3, the PL peak is centered at 560 nm with a PLQY of 47.3%, while the PL peak of Cs3Cu2I5 is located at 440 nm with an unprecedently high PLQY of 95.3%. Furthermore, the intermediate-state CsCu2I3/Cs3Cu2I5 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.

Improved Energy Transfer in Mn-Doped Cs3Cu2I5 Microcrystals Induced by Localized Lattice Distortion

With nontoxicity and high emission efficiency, luminescent copper(I)-based halides have attracted much attention as alternatives for lead-based perovskites in photoelectric domains. However, extending the emission wavelength by doping with Mn²⁺ in a facile way is still a challenge. In this work, Mn²⁺-doped Cs₃Cu₂I₅ microcrystals were synthesized by a mild solution method, and double emission bands from self-trapped excitons (STEs) and Mn²⁺ peaking at 445 and 560 nm, respectively, were observed. More importantly, further introduction of alkali metal ions (Rb⁺, K⁺, Na⁺) considerably promoted the luminescence performance of the Cs₃Cu₂I₅-Mn microcrystals. The STE → Mn²⁺ energy transfer efficiency of the typical sample doped with Na⁺ increased from ∼0 to 21.30%, and the photoluminescence quantum yield (PLQY) increased from 47.32% to 62.06%. The detailed structural and optical characterizations combined with DFT calculations proved that the doping with alkali metal ions causes lattice distortion and enhances the coupling between [MnI₄] and [CuI₄] tetrahedra, thus promoting the energy transfer efficiency and the PLQY.

Mn2+ induced significant improvement and robust stability of radioluminescence in Cs3Cu2I5 for high-performance nuclear battery

Fluorescent type nuclear battery consisting of scintillator and photovoltaic device enables semipermanent power source for devices working under harsh circumstances without instant energy supply. In spite of the progress of device structure design, the development of scintillators is far behind. Here, a Cs₃Cu₂I₅: Mn scintillator showing a high light yield of ~67000 ph MeV⁻¹ at 564 nm is presented. Doping and intrinsic features endow Cs₃Cu₂I₅: Mn with robust thermal stability and irradiation hardness that 71% or >95% of the initial radioluminescence intensity can be maintained in an ultra-broad temperature range of 77 K-433 K or after a total irradiation dose of 2590 Gy, respectively. These superiorities allow the fabrication of efficient and stable nuclear batteries, which show an output improvement of 237% respect to the photovoltaic device without scintillator. Luminescence mechanisms including self-trapped exciton, energy transfer, and impact excitation are proposed for the anomalous dramatic radioluminescence improvement. This work will open a window for the fields of nuclear battery and radiography.

Fluorescent-type nuclear batteries are a promising semi-permanent power source, but performance is hindered by scintillator development. Here the authors report a scintillator with high light yield and stability, which leads to improved performance.

Investigation of spectral output of Er3+ and Yb3+/Er3+ doped TeO2–ZnO–BaO glasses for photonic applications

Er³⁺ and Yb³⁺/Er³⁺ doped TeO₂–ZnO–BaO glasses were synthesized using the melt quenching technique with two different Er³⁺ concentrations for photonic applications.

Thermochromic Luminescent Nanomaterials Based on Mn4+/Tb3+ Codoping for Temperature Imaging with Digital Cameras

A new thermographic nanocrystalline Sr4Al14O25:Mn4+,Tb3+ phosphor was developed, and the concentrations of both dopants and the synthesis conditions were optimized. The combination of the thermally quenched luminescence from the Mn4+ ions to the almost temperature-independent emission from Tb3+ provides a sensitive luminescent thermometer (SR = 2.8%/°C at 150 °C) with strong emission color variability. In addition, a figure of merit for this luminescence thermochromism was proposed, as the relative sensitivities of the x and y CIE coordinates, which for this phosphor reaches at 150 °C SR(x) = 0.6%/°C and SR(y) = 0.4%/°C, respectively. Noncontact thermal imaging was demonstrated with this phosphor using a single consumer digital camera and exploiting the ratio of red (R) and green (G) channels of the RGB images, thereby confirming the high application potential of Sr4Al14O25:Mn4+,Tb3+ nanocrystals for thermal sensing and mapping.

All-inorganic copper(i)-based ternary metal halides: promising materials toward optoelectronics

All-inorganic lead halides, including CsPbX₃ (X = Cl, Br, I), have become important candidate materials in the field of optoelectronics. However, the inherent toxicity of metal lead and poor material stability have hindered further applications of traditional metal halides, CsPbX₃. Therefore, copper(i)-based ternary metal halides are expected to become promising substitutes for traditional metal halides because of their nontoxicity, excellent optical properties and good stability under ambient conditions. This article reviews the recent development of all-inorganic low-dimensional copper(i)-based ternary metal halides by introducing their various synthesis methods, crystal structures, properties and their optoelectronic applications. In addition, the prospects for future challenges and the potential significance of copper(i)-based ternary metal halides in optoelectronic fields are presented.

N, P-co-doped carbon dots as a dual-mode colorimetric/ratiometric fluorescent sensor for formaldehyde and cell imaging via an aminal reaction-induced aggregation process

Novel colorimetric and ratiometric fluorometric dual-mode N, P-co-doped carbon nanodots, BPEI-CDs, for highly sensitive and selective detection of formaldehyde (FA) were successfully prepared from N-(phosphonomethyl)iminodiacetic acid (PMIDA) and branched polyethyleneimine (BPEI). The treatment of FA caused a remarkable linear enhancement of ratiometric fluorescence (F_501 nm/F_408 nm) in a wide range of 0-40 μM with a detection limit (LOD) of 0.47 μM (3σ/k), along with distinct color changes from colorless to light yellow. Mechanistic study shows that this electron-rich system, formed by the cooperative roles of N and P, promoted the FA-induced Schiff bases formation reaction, which contributed to the CD aggregation-induced emission (AIE) "turn-on" response and enhancement of π-conjugation-induced bathochromic behaviors. Furthermore, N, P-co-doped BPEI-CDs were successfully applied to the determination of FA in bean sprout samples. Using the standard addition method, the recoveries ranged from 96.9 to 101.8%, and the relative standard deviation (RSD) was in the range 2.23 to 3.21%. The application for intracellular FA sensing further verified that this novel nanoprobe may offer a new venue for the design of simple, low-cost, and sensitive biosensors. Graphical abstract.