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Herein, we successfully prepared Te4+-doped zero-dimensional (0D) cesium zinc chloride (Cs 2 ZnCl 4) crystals using solvothermal method. The structural and luminescence properties of Cs 2 ZnCl 4 : Te4+ crystals have been investigation in detail by means of spectral experiments and density functional theory calculations. The Cs 2 ZnCl 4 : Te4+ crystal exhibits broadband yellow emission at 580 nm with a photoluminescence quantum yield (PLQY) of 33.7% and a large full width at half maximum about 117 nm, of which emission is attributed to self-trapped excitons resulting from lattice vibration of the distorted structure. At low temperature, the PL intensity of Cs 2 ZnCl 4 : Te4+ crystals increase unusually, which is mainly related to the triplet state emission mechanism. In addition, PL lifetime is strongly temperature-dependent, and we calculated the maximum relative sensitivity is 0.93 %K−1 at 105–120 K and the maximum absolute sensitivity is 29 ns K−1 at 130 K. These findings not only provide important clues to the optical properties of 0D metal halides, but also highlight its significant potential in non-contact optical thermometry technology. [Display omitted] • Te4+ doped Cs 2 ZnCl 4 crystals are successfully synthesized by solvothermal method. • At low temperatures, Cs 2 ZnCl 4 : Te4+ crystals exhibit unusual luminescent behavior. • The maximum values of relative and absolute sensitivity are obtained as 0.93 % K−1 and 29 ns K−1, respectively. [ABSTRACT FROM AUTHOR]

Luminescent materials with multi-emission features are difficult to be replicated, which are highly desirable for advanced anti-counterfeiting. Here, we report the pioneering synthesis of Mn2+/Yb3+/Er3+ tri-doped Cs2Ag0.8Na0.2InCl6 double perovskites (MYE-DP), which exhibit photoluminescence (PL) covering from visible to near-infrared (NIR). The PL colors under excitations of 254 and 365 nm are notably different due to the changed relative emission intensities of self-trapped excitons (STEs) and Mn2+ d–d transition. Moreover, under the excitation of a NIR laser, the MYE-DP exhibits upconversion (UC) emissions of Mn2+ and Er3+. After ceasing the excitation, the long-lived trapped electrons can be thermally released to Mn2+ and Er3+ ions, resulting in both visible and NIR afterglow. Based on multi-modal emissions of the MYE-DP, we demonstrate a five-level anti-counterfeiting strategy, which significantly increases the anti-counterfeiting security. In addition, this work provides valuable insights into the energy transfer between STEs, Mn2+, Ln3+, and traps, laying a solid foundation for future development of new lead-free perovskites. [ABSTRACT FROM AUTHOR]

Efficient and stable scintillators play a crucial role in X‐ray detection applications. To enhance the luminescence efficiency under X‐ray excitation, the incorporation of multiple emission centers into scintillators is widely explored. Here, it is found that the cesium copper halide Cs5Cu3Cl6I2 exhibits dual emission centers, enabling high‐performance scintillators with an X‐ray light yield of 49000 photon MeV−1 and a low detection limit of 4 nGy s−1. The emissions of Cs5Cu3Cl6I2 are from intrinsic self‐trapped exciton (STE) and Frenkel defect‐assisted STE. High‐energy X‐rays can induce an increased fraction of Frenkel defect‐assisted STEs, which can serve as an effective scintillation channel. Furthermore, large‐area flexible scintillators with a high resolution of 18 lp mm−1 are developed, making them suitable for X‐ray imaging applications. These findings offer promising insights for developing more efficient scintillators. [ABSTRACT FROM AUTHOR]

The outstanding photovoltaic characteristics of lead halide perovskites have made them a potential class of materials for upcoming optoelectronic applications. However, a major obstacle to the practical use of lead halide perovskites is the inherent toxicity and low environmental stability of lead. The exploration and development of nontoxic and stable alternatives for lead halide perovskites has therefore become an urgent and critical goal in the field of photovoltaics. In this paper, blue lead-free Cs3Cu2I5 nanocrystals (NCs) with bright emission were prepared by using KI as a metal additive through an improved thermal injection strategy. A breakthrough in the previous photoluminescence quantum (PLQY) yield of 97.2% was achieved when the content of KI was optimized to be 8%. Detailed experimental and theoretical studies have also been combined to conclude that the KI additive acts to passivate surface defects and that the broad-spectrum blue emission originates from self-trapped excitons. When combined with commercial indium tin oxide (ITO), the device may achieve broad-spectrum blue electroluminescence. Its low production cost and simple structure are its main features. Furthermore, we were able to improve the utilization of high-energy ultraviolet energy and overcome the weak absorption of short-wavelength silicon-based solar cells by using nanocrystals as down-conversion luminescent materials in conjunction with silicon-based solar cells. This increased the photoelectric conversion efficiency (PCE) for the solar cells through approximately 0.5%. The result was achieved through the principle of down-conversion. Therefore, fully inorganic metal halide Cs3Cu2I5: K+ nanocrystals have great potential for future electroluminescence and photovoltaic applications. [ABSTRACT FROM AUTHOR]

0D lead‐free metal halides with stimuli‐responsive photoluminescence (PL) have attracted great attention as promising smart materials for advanced anticounterfeiting and information encryption. However, designing high‐performance stimuli‐responsive metal halides remains a challenge. Herein, a solvent guest tuning strategy to develop stimuli‐responsive 0D metal halides is proposed. Three novel highly yellow‐emissive host‐guest systems, TMA2SbCl5·X (TMA: (CH3)4N+, X = DMSO, DMF, and MeCN) are synthesized. Under heat stimuli, TMA2SbCl5·X (X = DMSO and DMF) exhibits PL on‐off switching, while TMA2SbCl5·MeCN shows PL color change from yellow to orange, due to structural phase transitions. Particularly, TMA2SbCl5·DMSO and TMA2SbCl5·MeCN demonstrate a fast response within 50 s at temperatures above 353 K. Detailed in situ XRD diffraction study unveils the role of guest solvent molecules in the regulation of structural phase transitions. For the first time, it is found that the host‐guest systems possess a guest‐dependent structural evolution that results in a different PL response to heat stimuli. In addition, moister can also trigger structural phase transition and induce PL on‐off switching. The remarkable stimuli response performance makes these hybrids promising for anticounterfeiting and encryption applications. These findings provide new insights for the development of stimuli‐responsive lead‐free metal halide materials. [ABSTRACT FROM AUTHOR]

Self‐trapped excitons (STEs) of lead‐free perovskites have aroused tremendous interest in remote optical thermometry due to strong exciton–phonon coupling and large Stokes shifts. Herein, a bright multimodal and multiplexed optical thermometer is constructed with high sensitivity (Sr) and self‐calibrating ability based on Cs2NaInCl6:Er3+ double perovskite, allowing for fast and simplified reading via mobile devices. Intriguingly, Er3+ doping not only shows the characteristic green emissions but also introduces nanoelectronic domains through a new localized valance band maximum and breaks the symmetry of In3+ site, which facilitates the generation of more STEs. The temperature‐sensitive blue emission of STEs and temperature‐insensitive green emission of Er3+ endow multimodal optical thermometry including time‐resolved and ratiometric readout schemes with a maximum Sr of 3.8% K−1, where an upconversion primary thermometry serves as a reference to calibrate other modes. Meanwhile, the designed thermometers show robust photostability, repeatability, and structural stability for long‐time working and storage. In addition, the remarkable thermochromic phenomenon from blue to green enables a quick color‐multiplexed thermography on a smartphone, which is utilized to capture real‐time 2D thermal imaging of microelectronic devices. This work demonstrates the great potential of lead‐free double perovskite for low‐cost and portable optical thermometry. [ABSTRACT FROM AUTHOR]

ns2 ions‐doped lead‐free perovskites have garnered significant attention for their potential in diverse optoelectronic applications, owing to their broad emission characteristics arising from self‐trapped excitons (STEs). Herein, high‐performance white light‐emitting diodes (WLEDs) for intelligent lighting are developed by Bi3+/Te4+co‐doped Cs2SnCl6. Effective energy transfer between the dual STE emissions results in tunable broadband emissions covering the full‐color region. Adjustable WLEDs containing cold‐ and warm‐white lighting are fabricated. The WLEDs have excellent luminescent performances coupled with adjustable correlated color temperatures of 6417 and 3829 K. This versatility allows them to meet lighting demand for different scenarios, which is essential for future WLEDs to achieve healthy lighting. In addition, the excellent white light emission characteristics can also be applied in the visible light communication (VLC) system, achieving a −3 dB bandwidth of 13.3 MHz and opening eye diagrams in the data rate range of 10–60 Mbps. This work represents a significant advancement toward building intelligent health lighting applications and achieving high‐quality light sources for VLC based on lead‐free perovskites. [ABSTRACT FROM AUTHOR]

Hybrid metal halides (HMHs) have emerged as a promising platform for optically functional crystalline materials, but it is extremely challenging to thoroughly elucidate the electron transition coupled to additional ligand emission. Herein, to discover sequences of lead‐free HMHs with distinct optically active metal cations are aimed, that is, Sb3+ (5s2) with the lone‐pair electron configuration and In3+ (4d10) with the fully‐filled electron configuration. (Me2NH2)4MCl6·Cl (Me = −CH3, M = Sb, In) exhibits the superior temperature/component‐dependent luminescence behaviors resulting from the competition transition between triplet‐states (Tn‐S0) self‐trapped excitons (STEs) of inorganic units and singlet‐state (S1‐S0) of organic cations, which is manipulated by the optical activity levels of [SbCl6]3− and [InCl6]3−. The bonding differences between Sb3+/In3+ and Cl− in terms of electronic excitation and hybridization are emphasized, and the different electron‐transition mechanisms are established according to the PL spectra at the extreme temperature of 5 to 305 K and theoretical calculations. By fine‐tuning the B‐site Sb3+/In3+ alloying, the photoluminescence quantum yield (PLQY = 81.5%) and stability are optimized at 20% alloying of Sb3+. This research sheds light on the rules governing PL behaviors of HMHs, as well as exploring the optical‐functional application of aviation temperature sensors and access‐control systems. [ABSTRACT FROM AUTHOR]

Stimuli‐responsive luminescent materials have attracted much research attention due to their wide application potential in various fields. Typically, the family of hydrated double perovskite A2MIIIX5·H2O shows unique emission color transformation between hydrated and dehydrated complexes, highlighting the application potential in advanced anti‐counterfeiting. Herein, two zero‐dimensional perovskites of Cs2YbCl5·H2O and Cs3YbCl6, are reported and broad‐band self‐trapped exciton recombination emission can be realized via external Sb3+ doping. Intriguingly, the Cs2YbCl5·H2O can be transformed to the dehydrated counterpart of Cs3YbCl6 through a facile methanol treatment at room temperature, leading to the emission color transformation from yellow to green. Notably, the green‐emissive Cs3YbCl6:Sb3+ delivers a high photoluminescence quantum yield of 67.3%. Leveraging the advantages of obvious methanol‐induced emission color transformation between Cs2YbCl5·H2O and Cs3YbCl6 at room temperature, Cs2YbCl5·H2O can be used in the field of high‐security‐level anti‐counterfeiting. [ABSTRACT FROM AUTHOR]

Scintillators have been widely used for high‐energy radiation imaging. It is in great demand and challenge to develop scintillator materials with fast decay time, high scintillation light yield, and low detection limit for high‐resolution imaging applications such as time‐of‐flight positron emission tomography. However, it is still a challenge to develop the ultrafast carrier dynamics to achieve 100% ultrafast decay time with high scintillation light yield. To meet the demand, a series of component‐tunable Cs2ZnCl4: x%Zr single crystals as promising ultrafast scintillators is successfully developed. With 8% of Zr‐dopant (Cs2ZnCl4: 8%Zr), the single crystal exhibits high light yield (28000 photons MeV−1) and low detection limit (51 nGy s−1) under X‐ray excitation. Photo‐induced transient absorption signals on sub‐nanosecond and nanosecond scales ensure almost 100% fast decay time (≈3 ns) in nanoseconds under γ‐ray excitation. In particular, the different radiative transition processes are achieved under ultraviolet and high‐energy radiation due to the tunable carrier dynamics from the shallow trapped state to the self‐trapped exciton (STE) state. [ABSTRACT FROM AUTHOR]

The low‐dimensional organic‐inorganic lead halide compound has garnered significant attention in recent times due to its exceptional optoelectronic properties. However, its application in the field of optoelectronics has been hindered by the toxicity of lead. Here, a novel inorganic‐organic compound [Epy]2[CuBr3] single crystal material with a 0D structure based on Cu(I) is introduced. The single crystal exhibits a broad band yellow luminescence, a significant Stokes shift, and a microsecond‐scale photoluminescence (PL) lifetime, which is mainly attributed to the self‐trapped excitons (STEs) excitation. In addition, the relevant PL spectra are measured at 78–348 K. The photoluminescence intensity decreases with increasing temperature due to strong electro‐phonon coupling. The exciton binding energy Eb of the crystal is 76.43 meV, and the Huang‐Rhys factor S is 40.55. It is worth noting that the crystal also shows a good response to X‐rays. Overall, [Epy]2[CuBr3] displays its good potential. [ABSTRACT FROM AUTHOR]

Luminescent Mn(II)‐based organic–inorganic hybrid halides have drawn attention as potential materials for sensing and photonics applications. Here, the synthesis and characterization of methylammonium (MA) manganese bromide ((MA)nBrxMn(H2O)2, (n = 1, 4 and x = 3, 6)) with different stoichiometries of the organic cation and inorganic counterpart, are reported. While the Mn2+ centers have an octahedral conformation, the two coordinating water molecules are found either in cis (1) or in trans (2) positions. The photophysical behavior of 1 reflects the luminescence of Mn2+ in an octahedral environment. Although Mn2+ in 2 also has octahedral coordination, at room temperature dual emission bands at ≈530 and ≈660 nm are observed, explained in terms of emission from Mn2+ in tetragonally compressed octahedra and self‐trapped excitons (STEs), respectively. Above the room temperature, 2 shows quasi‐tetrahedral behavior with intense green emission, while at temperatures below 140 K, another STE band emerges at 570 nm. Time‐resolved experiments (77–360 K) provide a clear picture of the excited dynamics. 2 shows rising components due to STEs formation equilibrated at room temperature with their precursors. Finally, the potential of these materials for the fabrication of color‐tunable down‐converted light‐emitting diode (LED) and for detecting polar solvent vapors is shown. [ABSTRACT FROM AUTHOR]

Halide perovskite light‐emitting diodes (LEDs) have made remarkable advancements in both efficiency and stability. However, when compared to green and red LEDs, blue perovskite LEDs still lag behind in terms of efficiency and stability. Presently, efficient blue LEDs primarily rely on lead‐based perovskites, which goes against the environmentally friendly practices and restricts potential industrial applications. Consequently, there has been a surge of interest in academic research toward developing blue LEDs using lead‐free perovskites. This paper provides a comprehensive review of the structural diversity of lead‐free perovskite derivatives used for blue emission, encompassing Sn‐, Zr‐, Bi‐, Sb‐, Cu‐, Zn‐based halides as well as double perovskites. Various material synthesis techniques are discussed, such as nanocrystal preparation and film preparation. Additionally, the photoluminescence properties for different energy band structures are outlined, along with the luminescence mechanism involving energy transfer and strategies for enhancing luminous efficiency. The advancement in efficiency and stability of lead‐free perovskite LEDs is also examined in this review. Finally, the current challenges and future opportunities in advancing research on blue lead‐free perovskite derivatives and their potential application in LED technology is emphasized. [ABSTRACT FROM AUTHOR]

Thermochromic materials, known for their unique ability to change optical properties with temperature, have broad applications, including in thermochromic light‐emitting diodes (LEDs). However, the scarcity of efficient and stable thermochromic phosphors limits their development. In this study, the development of a novel thermochromic phosphor based on zero‐dimensional (0D) inorganic metal halides is reported. The 0D Cs2ZnBr4:Ag+ phosphors show thermally enhanced self‐trapped exciton (STE) emission across a wide temperature range from 120 to 300 K with the emitted wavelength changing correspondingly. Temperature‐dependent photoluminescence (PL), time‐resolved PL, and density functional theory calculations confirm that the thermally enhanced STE emission originates from the passivated defect/traps in Cs2ZnBr4 and the thermally assisted energy transfer from the host to STEs formed by [AgBr4]3– tetrahedron with matrix phonons complementing the energy mismatch. Furthermore, the reversible thermochromic LEDs based on Cs2ZnBr4:Ag+ phosphors are successfully prepared. Overall, these findings provide a future design of high‐efficiency thermally enhanced luminescent materials and pave a new way for developing thermochromic materials for functional LED illumination. [ABSTRACT FROM AUTHOR]

With strong electron–phonon coupling, self‐trapped excitons (STEs) are typically formed in perovskite materials, and radiative recombination of STEs can produce broadband emission with large Stokes shifts. STEs are essential to further improve the optoelectronic properties of materials. Surprisingly, 2D system is the edge case, with low even no self‐trapping barriers, leading to effortless formation of STEs. In this work, 2D strontium titanate (SrTiO3) with defects is prepared using supercritical carbon dioxide (SC CO2) and its carrier transport and transition are studied. The appearance of wide photoinduced positive absorption signals in the femtosecond transient absorption spectra is direct evidence for the formation of STEs. The presence of STEs is further supported by the increased Stokes shift and full width at half maximum in the steady‐state photoluminescence spectra. [ABSTRACT FROM AUTHOR]

Mn2+ doping has been adopted as an efficient approach to regulating the luminescence properties of halide perovskite nanocrystals (NCs). However, it is still difficult to understand the interplay of Mn2+ luminescence and the matrix self-trapped exciton (STE) emission therein. In this study, Mn2+-doped CsCdCl3 NCs are prepared by hot injection, in which CsCdCl3 is selected because of its unique crystal structure suitable for STE emission. The blue emission at 441 nm of undoped CsCdCl3 NCs originates from the defect states in the NCs. Mn2+ doping promotes lattice distortion of CsCdCl3 and generates bright orange-red light emission at 656 nm. The energy transfer from the STEs of CsCdCl3 to the excited levels of the Mn2+ ion is confirmed to be a significant factor in achieving efficient luminescence in CsCdCl3:Mn2+ NCs. This work highlights the crucial role of energy transfer from STEs to Mn2+ dopants in Mn2+-doped halide NCs and lays the groundwork for modifying the luminescence of other metal halide perovskite NCs. [ABSTRACT FROM AUTHOR]

Zero-dimension (0D) lead-free metal halide perovskites have attracted great attention because of their outstanding photophysical properties. However, the development of tunable-color-temperature white-light emission in single perovskite phosphors is still a challenge. Herein, a dual-band tunable multicolor emitters based on ns2 ions (Bi3+ and Te4+) codoped with a 0D hybrid perovskite derivative (C4H12N)2HfCl6 is reported. The prepared (C4H12N)2HfCl6:Bi3+/Te4+ samples exhibit broad dual-band emission originating from the dopant self-trapped excitons of [BiCl6]3– and [TeCl6]2–, respectively. By virtue of the energy transfer from blue-emitting (Bi3+) to yellow-emitting (Te4+), tunable dual-emission white-light emission covering the entire visible region is achieved. Meanwhile, Bi3+/Te4+-codoped perovskites exhibit unique excitation-dependent emission, and a wide color gamut can be obtained by precisely controlling the excitation wavelength, which corresponds to the color hue evolution from warm white to blue, then to white, and finally to orange. These findings provide fundamental insight into multicolor emission in the Bi3+/Te4+-codoped systems and open up more opportunities for multifunctional applications. [ABSTRACT FROM AUTHOR]

Organic–inorganic hybrid Ge(II)‐based metal halides have garnered significant interest due to their intriguing photophysical properties and environmentally friendly characteristics. However, challenges such as poor stability, low emission intensity, and a complex synthesis process have hindered their widespread application. In addressing these issues, a breakthrough in the large‐scale production of Sb3+‐doped Ge(IV)‐based metal halide (C13H14N3)2GeCl6 phosphors at room temperature through a straightforward solution method is presented. The synthesized compound exhibits a remarkable bright broad yellow emission band at 590 nm, boasting a photoluminescence quantum efficiency of 99.53 ± 0.06% the highest among Ge(IV)‐based metal halides. Notably, the introduction of Sb3+ induces the formation of Jahn–Teller‐like self‐trapped excitons in [SbCl6]3− species, attributable to lattice distortion and strong electron–phonon coupling. Consequently, Sb3+‐doped (C13H14N3)2GeCl6 demonstrates a large Stokes shift (221 nm) and a prolonged decay lifetime (3.06 μs). Furthermore, the Sb3+‐doped compound exhibits commendable chemical‐ and photostability, prompting exploration in applications such as white light‐emitting diodes and latent fingerprint detection. This work not only provides a practical approach for designing economically viable, environmentally friendly, and highly efficient emission phosphors but also paves the way for novel directions in their expanded application. [ABSTRACT FROM AUTHOR]

Integrating self‐trapped excitons (STEs), dopants, and defect levels in a single‐component metal halide perovskite will be of significance for tunable multimode luminescence and photochromism. Here, a platform utilizing interactions of STEs, defects, and alien dopants in CsCdCl3 by a heterovalent doping strategy is demonstrated, in which the photoluminescence quantum efficiency is improved, and more importantly, the emissions can be manipulated statically and dynamically by dopants and changing excitation wavelength/irradiation time. Meanwhile, the presence of carrier trapping and de‐trapping processes leads to bright orange–near‐infrared persistent luminescence and photochromic behaviors, which can be quickly erased by white light, enabling visual displays and codable in dark and bright dual‐fields. Inspired by these versatile optical characteristics of doped luminescent metal halides, a multilevel encryption and anti‐counterfeiting platform with the advantages of nondestructive and convenient authentication is constructed. [ABSTRACT FROM AUTHOR]

Low-dimensional metal halides with efficient luminescence properties have received widespread attention recently. However, nontoxic and stable low-dimensional metal halides with efficient blue emission are rarely reported. We used a solvothermal synthesis method to synthesize tetravalent zirconium ion-doped all-inorganic zero-dimensional Cs2ZnCl4 for the first time. Bright blue emission in the range of 370 nm–700 nm with a emission maximum at 456 nm was observed in Zr4+:Cs2ZnCl4 accompanied by a large Stokes shift, which was due to self-trapped excitons (STEs) caused by the lattice vibrations of the twisted structure. Simultaneously, the PLQY of Zr4+:Cs2ZnCl4 achieve an impressive 89.67%, positioning it as a compelling contender for future applications in blue-light technology. [ABSTRACT FROM AUTHOR]

The vacancy-ordered quadruple perovskite Cs4CdBi2Cl12, as a newly-emerging lead-free perovskite system, has attracted great research interest due to its excellent stability and direct band gap. However, the poor luminescence performance limits its application in light-emitting diodes (LEDs) and other fields. Herein, for the first time, an Ag+ ion doping strategy was proposed to greatly improve the emission performance of Cs4CdBi2Cl12 synthesized by hydrothermal method. Density functional theory calculations combined with experimental results evidence that the weak orange emission from Cs4CdBi2Cl12 is attributed to the phonon scattering and energy level crossing due to the large lattice distortion under excited states. Fortunately, Ag+ ion doping breaks the intrinsic crystal field environment of Cs4CdBi2Cl12, suppresses the crossover between ground and excited states, and reduces the energy loss in the form of nonradiative recombination. At a critical doping amount of 0.8%, the emission intensity of Cs4CdBi2Cl12:Ag+ reaches the maximum, about eight times that of the pristine sample. Moreover, the doped Cs4CdBi2Cl12 still maintains excellent stability against heat, ultraviolet irradiation, and environmental oxygen/moisture. The above advantages make it possible for this material to be used as solid-state phosphors for white LEDs applications, and the Commission International de l'Eclairage color coordinates of (0.31, 0.34) and high color rendering index of 90.6 were achieved. More importantly, the white LED demonstrates remarkable operation stability in air ambient, showing almost no emission decay after a long working time for 48 h. We believe that this study puts forward an effective ion-doping strategy for emission enhancement of vacancy-ordered quadruple perovskite Cs4CdBi2Cl12, highlighting its great potential as efficient emitter compatible for practical applications. [ABSTRACT FROM AUTHOR]

Lead-free halide double perovskites are considered as one of the most promising materials in optoelectronic devices, such as solar cells, photodetectors, and light-emitting diodes (LEDs), due to their environmental friendliness and chemical stability. However, the extremely low photoluminescence quantum yield (PLQY) of self-trapped excitons (STEs) emission from lead-free halide double perovskites impedes their applications. Herein, Sb3+ ions were doped into rare-earth-based double perovskite Cs2NaScCl6 single crystals (SCs), resulting in a large enhancement of PLQY from 12.57% to 87.37%. Moreover, by co-doping Sb3+ and Ho3+ into Cs2NaScCl6 SCs, the emission color can be tuned from blue to red, due to an efficient energy transfer from STEs to Ho3+ ions. Finally, the synthesized sample was used in multicolor LED, which exhibited excellent stability and optical properties. This work not only provides a new strategy for improving the optical properties of Cs2NaScCl6 SCs, but also suggests its potential application in multicolor LEDs. [ABSTRACT FROM AUTHOR]

Low‐dimensional organic–inorganic metal halides (OIMHs) have emerged as promising light emitters due to their broadband emission originating from self‐trapped excitons (STE), especially for Cu‐based OIMHs. Herein, Cu(I)‐based OIMH with a structure of (TPP)2Cu4I6·2DMSO (TPP stays for tetraphenylphosphonium, and DMSO – for dimethyl sulfoxide) has been synthesized, both in form of single crystals and as a microcrystalline powder. This compound exhibits a broadband green emission with a peak at 515 nm and a full width at half‐maximum of 78 nm, and a near‐unity photoluminescence quantum yield of 99.5%. Experimental data supported by theoretical calculations indicate that the STE emission is responsible for the green emission with a long lifetime of 2.53 µs. Down‐conversion light‐emitting device with a high luminous efficiency of 50 lm W−1 based on this compound have been fabricated, and white light has also been achieved with a high color rendering index of 96.7. Moreover, green emissive (TPP)2Cu4I6·2DMSO is utilized in scintillators for X‐ray detection and imaging, and as a luminescent ink for encryption applications. [ABSTRACT FROM AUTHOR]

Abstract Low‐dimensional hybrid halide perovskites represent a promising class of materials in optoelectronic applications because of strong broad self‐trapped exciton (STE) emissions. However, there exists a limitation in designing the ideal A‐site cation that makes the material satisfy the structure tolerance and exhibit STE emission raised by the appropriate electron–phonon coupling effect. To overcome this dilemma, we developed an inorganic metal‐organic dimethyl sulfoxide (DMSO) coordinating strategy to synthesize a series of zero‐dimensional (0D) Sb‐based halide perovskites including Na3SbBr6·DMSO6 (1), AlSbBr6·DMSO6 (2), AlSbCl6·DMSO6 (3), GaSbCl6·DMSO6 (4), Mn2Sb2Br10·DMSO13 (5) and MgSbBr5·DMSO7 (6), in which the distinctive coordinating A‐site cation [Am‐DMSO6]n+ efficiently separate the [SbXz] polyhedrons. Advantageously, these materials all exhibit broadband‐emissions with full widths at half maxima (FWHM) of 95–184 nm, and the highest photoluminescent quantum yield (PLQY) of 3 reaches 92%. Notably, compounds 2–4 are able to remain stable after storage of more than 120 d. First‐principles calculations indicate that the origin of the efficient STE emission can be attributed to the localized distortion in [SbXz] polyhedron upon optical excitation. Experimental and calculational results demonstrate that the proposed coordinating strategy provides a way to efficiently expand the variety of novel high‐performance STE emitters and continuously regulate their emission behaviors.

Abstract Luminescent Mn(II)‐based organic–inorganic hybrid halides have drawn attention as potential materials for sensing and photonics applications. Here, the synthesis and characterization of methylammonium (MA) manganese bromide ((MA)nBrxMn(H2O)2, (n = 1, 4 and x = 3, 6)) with different stoichiometries of the organic cation and inorganic counterpart, are reported. While the Mn2+ centers have an octahedral conformation, the two coordinating water molecules are found either in cis (1) or in trans (2) positions. The photophysical behavior of 1 reflects the luminescence of Mn2+ in an octahedral environment. Although Mn2+ in 2 also has octahedral coordination, at room temperature dual emission bands at ≈530 and ≈660 nm are observed, explained in terms of emission from Mn2+ in tetragonally compressed octahedra and self‐trapped excitons (STEs), respectively. Above the room temperature, 2 shows quasi‐tetrahedral behavior with intense green emission, while at temperatures below 140 K, another STE band emerges at 570 nm. Time‐resolved experiments (77–360 K) provide a clear picture of the excited dynamics. 2 shows rising components due to STEs formation equilibrated at room temperature with their precursors. Finally, the potential of these materials for the fabrication of color‐tunable down‐converted light‐emitting diode (LED) and for detecting polar solvent vapors is shown.

With strong electron–phonon coupling, self‐trapped excitons (STEs) are typically formed in perovskite materials, and radiative recombination of STEs can produce broadband emission with large Stokes shifts. STEs are essential to further improve the optoelectronic properties of materials. Surprisingly, 2D system is the edge case, with low even no self‐trapping barriers, leading to effortless formation of STEs. In this work, 2D strontium titanate (SrTiO3) with defects is prepared using supercritical carbon dioxide (SC CO2) and its carrier transport and transition are studied. The appearance of wide photoinduced positive absorption signals in the femtosecond transient absorption spectra is direct evidence for the formation of STEs. The presence of STEs is further supported by the increased Stokes shift and full width at half maximum in the steady‐state photoluminescence spectra.

Most of current metal halide materials, including all inorganic and organic–inorganic hybrids, are crystalline materials with poor workability and plasticity that limit their application scope. Here, we develop a novel class of materials termed polymeric metal halides (PMHs) through introducing polycations into antimony‐based metal halide materials as A‐site cations. A series of PMHs with orange‐yellow broadband emission and large Stokes shift originating from inorganic self‐trapped excitons are successfully prepared, which meanwhile exhibit the excellent processability and formability of polymers. The versatility of these PMHs is manifested as the broad choices of polycations, the ready extension to manganese‐ and copper‐based halides, and the tolerance to molar ratios between polycations and metal halides in the formation of PMHs. The merger of polymer chemistry and inorganic chemistry thus provides a novel generic platform for the development of metal halide functional materials. [ABSTRACT FROM AUTHOR]

ABX3 halide–perovskites (HPs) have emerged as promising alternatives for optoelectronic devices owing to their excellent properties and low cost. Generally, A is either Cs or an organic molecule while B is Pb, or Sn and X = I, Br, or Cl. Here, ab initio calculations on K‐based new HP with X as a mixture of F and Cl are performed. Solid‐state synthesis leads to a mixed‐KPbF2Cl HP with an orthorhombic structure as determined from X‐ray diffraction and energy‐dispersive X‐ray spectroscopy. The high formation energy (−0.546 eV atom−1) shows excellent stability of this HP. Scanning electron microscopy reveals rodlike structures while X‐ray photoelectron spectroscopy is performed for chemical analysis. Diffuse reflectance shows it to have a wide bandgap of ≈4 eV, in good agreement with the band‐structure calculations. Further, a strong photoluminescence peak is found at ≈340 nm for radiative recombination of free excitons along with a broad emission peaking at ≈450 nm owing to the involvement of self‐trapped excitons associated with lattice distortion. The finding of this stable HP can lead to high‐frequency applications, along with other applications such as transparent and low‐loss optical windows, prisms, etc., as well as development of novel optical materials by doping. [ABSTRACT FROM AUTHOR]

Rb2Cu(Cl,Br)3 crystals were synthesized by the slow cooling method and their photoluminescence (PL) and scintillation properties were evaluated. PL emission peaks at 390 nm due to the recombination of excitons were observed, and the PL quantum yields of Rb2CuCl3, Rb2Cu(Cl0.5,Br0.5)3, and Rb2CuBr3 were 91.2, 95.3, and 96.3%, respectively. PL decay curves were approximated using a single exponential function model, and the obtained decay time constants were 15-66 µs. Under X-ray irradiation, the scintillation emission peaks of the samples were observed at 390 nm, and the decay times were 11-63 µs. The afterglow levels at 20 ms after X-ray irradiation were calculated to be 30-450 ppm. Rb2CuCl3 showed the highest scintillation light yield of 11000 photons/MeV among the samples when calculated from the pulse height spectra of 137Cs γ-rays (662 keV). [ABSTRACT FROM AUTHOR]

Copper halide semiconductors are attracting extensive attention due to their nontoxic composition and excellent optoelectronic properties. Most so far are prepared via solution methods; however, grain boundaries and defects existing in those products hinder their further practical applications in solid‐state devices. In this work, CsCu2I3 halides with 1D crystal structure are initially prepared by a vapor phase deposition method. The large Stokes shift coupling with a long photoluminescence decay time (112 ns) suggests the existence of a self‐trapped exciton process in these CsCu2I3 nanowires, responsible for the yellow light emission emerging at 570 nm. UV photodetectors based on individual CsCu2I3 nanowires that are constructed via an etching‐free dry transfer route reveal a responsivity of 122 mA W−1 and rise/decay times of 203/223 ms (310 nm, 5 V bias), comparable to or better than those congeneric UV sensors made of other lead‐free halides. These CsCu2I3 nanowire‐based photodetectors also reveal good stability in the atmosphere (RH = 60–70%, 17 °C), benefitting from their fourfold coordination environment of Cu(I) atoms in the 1D crystal structure. These results imply the technical potential of manufacturing low‐dimensional lead‐free halide semiconductors for next‐generation green optoelectronics. [ABSTRACT FROM AUTHOR]

In the era of intelligence, the output colors of foundational phosphors are expected to be controlled by programs, while current activators‐determined afterglow candidates with fixed spectral channel have limitations in creating customized colors. Here, a long‐lived warm‐white emission is successfully demonstrated originating from self‐trapped excitons (STEs) in non‐toxic Cs2NaInCl6:Ag,Bi, ranging from 400 to 850 nm, of which the afterglow color can be easily customized using filters. This investigation indicates that 3% of Ag alloying breaks the dark STEs and introduces traps for efficient afterglow, while 3% Bi doping further improves the quantum yield to ≈100% and greatly enhances afterglow by ≈100‐fold compared with the initial intensity, allowing for an impressive afterglow persistence of over 20,000 s. Intriguingly, the self‐trapped defect bands from Jahn‐Teller distortions are prolonged from hundreds of femtoseconds to several hours, and they are first detected in the steady‐state absorption spectra after the cessation of excitation sources, contributing to the concluded dynamic afterglow model for STEs. And its intelligent application is corroborated by designed multi‐channel information system. These findings offer a novel scheme for understanding dynamic luminescence of STEs and supply an exemplification of designing white afterglow phosphors. [ABSTRACT FROM AUTHOR]

Broadband emission induced by self‐trapped excitons (STEs) in double halide perovskites (DHPs) has received continuous attention in recent years. However, the comprehensive understanding of the STEs formation mechanism is still in its early stage. The corresponding roles of different B‐site cations also remain unclear in these advanced materials. The lack of an effective STEs database for DHPs hinders the efficient discovery of potential optoelectronic materials with strong STEs. Herein, a systematic STEs database is built for DHPs through density functional theory (DFT) calculations and proposed a highly efficient predictive machine learning (ML) model of the Huang–Rhys factor S for the first time. Results reveal the different contributions of two B‐site metal cations to the formation of STEs in DHPs, which helps to understand the in‐depth nature of STEs. Based on the accurate predictions of the effective phonon frequency ωLO$\left(\omega\right)_{\text{LO}}$ , it is further realized that the prediction of S without conducting the time‐consuming phonon property calculations of DHPs offers new opportunities for exploring the STEs. Combining DFT calculations and ML techniques, this study supplies an effective approach to efficiently discover the potential novel optoelectronic materials, which provides important guidance for the future exploration of promising solid‐state phosphors. [ABSTRACT FROM AUTHOR]

Organic–inorganic hybrid Ge(II)‐based metal halides have garnered significant interest due to their intriguing photophysical properties and environmentally friendly characteristics. However, challenges such as poor stability, low emission intensity, and a complex synthesis process have hindered their widespread application. In addressing these issues, a breakthrough in the large‐scale production of Sb3+‐doped Ge(IV)‐based metal halide (C13H14N3)2GeCl6 phosphors at room temperature through a straightforward solution method is presented. The synthesized compound exhibits a remarkable bright broad yellow emission band at 590 nm, boasting a photoluminescence quantum efficiency of 99.53 ± 0.06% the highest among Ge(IV)‐based metal halides. Notably, the introduction of Sb3+ induces the formation of Jahn–Teller‐like self‐trapped excitons in [SbCl6]3− species, attributable to lattice distortion and strong electron–phonon coupling. Consequently, Sb3+‐doped (C13H14N3)2GeCl6 demonstrates a large Stokes shift (221 nm) and a prolonged decay lifetime (3.06 μs). Furthermore, the Sb3+‐doped compound exhibits commendable chemical‐ and photostability, prompting exploration in applications such as white light‐emitting diodes and latent fingerprint detection. This work not only provides a practical approach for designing economically viable, environmentally friendly, and highly efficient emission phosphors but also paves the way for novel directions in their expanded application.

Highlights High-quality Sn2+/Mn2+-co-doped Rb4CdCl6 single crystals and powders were prepared and showed high-performance dual-emission white light with near-unity photoluminescence quantum yield. Short-range and extremely strong interactions between Sn2+ and Mn2+ were observed that lead to an intriguing ultra-high-efficiency Dexter energy transfer process from adjacent Sn2+ ions to Mn2+ ions. The dual-emission intensities were tuned flexibly by varying the fractions of Sn2+ and Sn–Mn pairs to balance their emission proportions for cold/warm white-light generation.

Broadband emission induced by self‐trapped excitons (STEs) in double halide perovskites (DHPs) has received continuous attention in recent years. However, the comprehensive understanding of the STEs formation mechanism is still in its early stage. The corresponding roles of different B‐site cations also remain unclear in these advanced materials. The lack of an effective STEs database for DHPs hinders the efficient discovery of potential optoelectronic materials with strong STEs. Herein, a systematic STEs database is built for DHPs through density functional theory (DFT) calculations and proposed a highly efficient predictive machine learning (ML) model of the Huang–Rhys factor S for the first time. Results reveal the different contributions of two B‐site metal cations to the formation of STEs in DHPs, which helps to understand the in‐depth nature of STEs. Based on the accurate predictions of the effective phonon frequency ω LO , it is further realized that the prediction of S without conducting the time‐consuming phonon property calculations of DHPs offers new opportunities for exploring the STEs. Combining DFT calculations and ML techniques, this study supplies an effective approach to efficiently discover the potential novel optoelectronic materials, which provides important guidance for the future exploration of promising solid‐state phosphors.

Ternary copper halide pseudo‐perovskites are in the forefront of research as potential active materials in light emission applications. The optoelectronic properties of these compounds can be fine‐tuned by the preparation of mixed‐halide compositions. After irradiation, self‐trapped excitonic states are formed in these materials. However, the emission from these self‐trapped states is not yet fully understood. In this work, mixed‐halide Cs3Cu2X5 films (where X: I and/or Br) are prepared by a simple spray‐coating method. Using ultraviolet photoelectron spectroscopy, the changes in optoelectronic properties are linked to the electronic structure of these materials. It is revealed that the incorporation of bromide into the lattice makes the emission process of these materials more vulnerable to trap states. By combining the different spectroscopic characterization techniques, the exact band structure of these compounds is determined, and the different processes are translated to the absolute energy scale. As an alternative excitation mechanism of self‐trapped states, α‐particles are used to induce radioluminescence response. The Cs3Cu2X5 films exhibit composite decay patterns, most likely attributed to a multitude of different trap state‐mediated recombination processes. [ABSTRACT FROM AUTHOR]

X‐ray luminescence spectra, thermally stimulated luminescence, and thermally stimulated conductivity of undoped cesium iodide (CsI) crystal are investigated in order to reach better understanding of the factors which govern the emission processes in this material. X‐ray luminescence spectra are recorded in the temperature range from 15 to 293 K. The low energy band at 2.2 eV emerging at heating above 120 K is assigned to the emission of residual impurities. Other two bands peaking at 3.6 and 4.3 eV at 15 K are attributed to the intrinsic emission of CsI due to the self‐trapped excitons (STEs). The parameters of the peaks observed in the thermally stimulated luminescence and conductivity of CsI crystal are calculated. Investigations of the thermally stimulated processes in CsI lead to the conclusion that the increase of luminescence of 4.3 eV observed above 70 K is due to release of trapped electrons, which subsequently interact with Vk centers and form on‐center STEs. The considerable ionic conductivity observed above 250 K can be explained by the influence of uncontrolled impurities of divalent metal atoms as well as Na+ ions. [ABSTRACT FROM AUTHOR]

Luminescent metal halides have attracted increasing attention because of their tunable emission and superior photoelectric properties. However, it is still challenging to achieve near‐infrared (NIR) emission from metal halides, which is important in applications such as food quality analysis and night vision. In this work, the broadband NIR emission is achieved by alloying Sn2+ into zero‐dimensional (0D) Cs2ZnBr4. The incorporating of Sn2+ cations enables the originally weakly luminescent Cs2ZnBr4 to exhibit an efficient broadband NIR emission. Upon photoexication, the optimized Sn2+ alloyed Cs2ZnBr4 (Cs2Zn0.875Sn0.125Br4) exhibits a highly efficient broadband NIR emission peaked around 700 nm, with a large Stokes shift of 323 nm, a full width at maximum of 177 nm, and a high quantum efficiency of around 41%. Spectroscopic and theoretical calculations unveil that the efficient NIR emission originates from the self‐trapping emission introduced by the Sn alloying. In addition to the high efficient broadband emission, the Sn2+ alloyed Cs2ZnBr4 also exhibits high thermal stability, retaining 78% of its initial intensity at 150 °C. The night vision application is demonstrated by using a light source fabricated by combining Sn2+ alloyed Cs2ZnBr4 phosphor with a 365 nm LED chip in the dark. [ABSTRACT FROM AUTHOR]

Single‐component metal halides with white light emission are highly attractive for solid‐state lighting applications, but it is still challenging to develop all‐inorganic lead‐free metal halides with high white‐light emission efficiency. Herein, by rationally introducing silver (Ag) into zero‐dimensional (0D) Cs3Cu2Br5 as new structural building unit, a one‐dimensional (1D) bimetallic halide Cs6Cu3AgBr10 is designed that emits strong warm‐white light with an impressive photoluminescence quantum yield (PLQY) of 94.5% and excellent stability. This structural transformation lowers the conduction band minimum while maintaining the localized nature of the valence band maximum, which is crucial in expanding the excitation spectrum and obtaining efficient self‐trapped excitons (STEs) emission simultaneously. Detailed spectroscopy studies reveal that the white‐light originates from triplet STEs emission, which can be remarkably improved by weakening the strong electron‐phonon coupling and thus suppressing phonon‐induced non‐radiative processes. Moreover, the interesting temperature‐dependent emission behavior, together with self‐absorption‐free property, make Cs6Cu3AgBr10 as sensitive luminescent thermometer and high‐performance X‐ray scintillator, respectively. These findings demonstrate a general approach to achieving effective single‐component white‐light emitters based on lead‐free, all‐inorganic metal halides, thereby opening up a new avenue to explore their versatile applications such as lighting, temperature detection and X‐ray imaging. [ABSTRACT FROM AUTHOR]

Doping impurity ions, such as lanthanide (Ln3+) ions, can introduce unique emissions over the visible and near infrared (NIR) region and enrich the optoelectronic properties for lead‐free perovskites. Here, tetragonal Cs3InCl6:Sb nanocrystals (NCs) with bright self‐trapped excitons (STEs) emission have been synthesized. Interestingly, tetragonal Cs3InCl6:1%Sb can transform into monoclinic Cs3InCl6:1%Sb and orthorhombic Cs2InCl5·H2O:1%Sb under different solvent triggers. Further, a series of Ln3+ ions are doped into Cs3InCl6:Sb NCs, along with the appearance of Ln3+ ions emissions over the visible and NIR region. Benefiting from the different photoluminescence (PL) origins of the STEs and Eu3+ emissions, Cs3InCl6:Sb,Eu NCs enable varied color delivery and exhibit great potential as anti‐counterfeiting materials. Meantime, Cs3InCl6:Sb,Nd NCs with strong NIR emissions demonstrate great potential for NIR light‐emitting diode (LED) applications. This work not only presents an effective strategy to tune the optoelectronic properties of lead‐free perovskites, but also provides insight into applications in the anticounterfeiting and LED fields. [ABSTRACT FROM AUTHOR]

Single‐source white light‐emitting diodes (WLEDs) with smart regulation of correlated color temperature (CCT) are indispensable for the next generation of WLEDs aimed at healthy and high‐quality illumination, where a suitable CCT value is closely related to our emotions and circadian rhythm. Herein, this work constructs a single‐component emission layer WLED with high performance for controllable daily lighting through Bi3+/Te4+ dual‐doped Cs2SnCl6 engineering. The efficient energy transfers between triple self‐trapped exciton states from Bi3+/Te4+ doping allow two tunable broadband emissions that can cover the full‐color region, thereby yielding a standout color‐rendering index of 94 for the fabricated WLED. The robust stability against heat, ultraviolet light, and environmental oxygen/water induces a long half‐lifetime of WLED up to 1104 h. Moreover, the dual‐doped strategy endows the emitter with excitation‐dependent luminescent characteristics, enabling the single emissive layer device to realize switching control of cold‐, positive‐, and warm‐white light by converting the excitation chip. Meanwhile, continuous regulation of CCT for different application scenarios can be achieved by adjusting the current of different chips. This work constitutes a solid step toward building single‐source WLEDs for smart and healthy lighting based on dual‐doped lead‐free metal halides. [ABSTRACT FROM AUTHOR]

Low-dimensional metal halides with efficient luminescence properties have received widespread attention recently. However, nontoxic and stable low-dimensional metal halides with efficient blue emission are rarely reported. We used a solvothermal synthesis method to synthesize tetravalent zirconium ion-doped all-inorganic zero-dimensional Cs2ZnCl4 for the first time. Bright blue emission in the range of 370 nm–700 nm with a emission maximum at 456 nm was observed in Zr4+:Cs2ZnCl4 accompanied by a large Stokes shift, which was due to self-trapped excitons (STEs) caused by the lattice vibrations of the twisted structure. Simultaneously, the PLQY of Zr4+:Cs2ZnCl4 achieve an impressive 89.67%, positioning it as a compelling contender for future applications in blue-light technology.

Abstract Single‐component metal halides with white light emission are highly attractive for solid‐state lighting applications, but it is still challenging to develop all‐inorganic lead‐free metal halides with high white‐light emission efficiency. Herein, by rationally introducing silver (Ag) into zero‐dimensional (0D) Cs3Cu2Br5 as new structural building unit, a one‐dimensional (1D) bimetallic halide Cs6Cu3AgBr10 is designed that emits strong warm‐white light with an impressive photoluminescence quantum yield (PLQY) of 94.5% and excellent stability. This structural transformation lowers the conduction band minimum while maintaining the localized nature of the valence band maximum, which is crucial in expanding the excitation spectrum and obtaining efficient self‐trapped excitons (STEs) emission simultaneously. Detailed spectroscopy studies reveal that the white‐light originates from triplet STEs emission, which can be remarkably improved by weakening the strong electron‐phonon coupling and thus suppressing phonon‐induced non‐radiative processes. Moreover, the interesting temperature‐dependent emission behavior, together with self‐absorption‐free property, make Cs6Cu3AgBr10 as sensitive luminescent thermometer and high‐performance X‐ray scintillator, respectively. These findings demonstrate a general approach to achieving effective single‐component white‐light emitters based on lead‐free, all‐inorganic metal halides, thereby opening up a new avenue to explore their versatile applications such as lighting, temperature detection and X‐ray imaging.

Highlights: High-quality Sn2+/Mn2+-co-doped Rb4CdCl6 single crystals and powders were prepared and showed high-performance dual-emission white light with near-unity photoluminescence quantum yield. Short-range and extremely strong interactions between Sn2+ and Mn2+ were observed that lead to an intriguing ultra-high-efficiency Dexter energy transfer process from adjacent Sn2+ ions to Mn2+ ions. The dual-emission intensities were tuned flexibly by varying the fractions of Sn2+ and Sn–Mn pairs to balance their emission proportions for cold/warm white-light generation. Single materials that exhibit efficient and stable white-light emission are highly desirable for lighting applications. This paper reports a novel zero-dimensional perovskite, Rb4CdCl6:Sn2+, Mn2+, which demonstrates exceptional white-light properties including adjustable correlated color temperature, high color rendering index of up to 85, and near-unity photoluminescence quantum yield of 99%. Using a co-doping strategy involving Sn2+ and Mn2+, cyan-orange dual-band emission with complementary spectral ranges is activated by the self-trapped excitons and d-d transitions of the Sn2+ and Mn2+ centers in the Rb4CdCl6 host, respectively. Intriguingly, although Mn2+ ions doped in Rb4CdCl6 are difficult to excite, efficient Mn2+ emission can be realized through an ultra-high-efficient energy transfer between Sn2+ and Mn2+ via the formation of adjacent exchange-coupled Sn–Mn pairs. Benefiting from this efficient Dexter energy transfer process, the dual emission shares the same optimal excitation wavelengths of the Sn2+ centers and suppresses the non-radiative vibration relaxation significantly. Moreover, the relative intensities of the dual-emission components can be modulated flexibly by adjusting the fraction of the Sn2+ ions to the Sn–Mn pairs. This co-doping approach involving short-range energy transfer represents a promising avenue for achieving high-quality white light within a single material. [ABSTRACT FROM AUTHOR]

Lead free double perovskites are highly promising optoelectronic materials, but most of them suffer from low photoluminescence quantum yield (PLQY) and poor stability. Herein, a series of lanthanide elements are used to prepare the lead free double perovskite Cs2NaLnX6 (X = Cl, Br, I) nanocrystals (NCs), acting as both the main structural ions and the 4f–4f emission centers. The mechanisms for the broadband emission of Cs2NaLnX6 NCs host are carefully studied based on various spectral results combining ultrafast dynamics detection and first‐principles calculation. The broadband emission of the Cs2NaLnX6 NCs originates from the self‐trapped exciton. The Cs2NaLnX6 NCs show remarkable water stability for more than eight months and favorable temperature and light irradiation stability (500 h). The PLQY for these materials is much higher than most of double perovskite materials, especially for Cs2NaEuCl6, which can approach to 70%. The white light emission from a single host material Cs2NaEuTbCl6 (Tb:Eu = 25:1) is obtained and applied to a light‐emitting diode device, with a good CIE (Commission International de L'Eclairage) coordinate of (0.334, 0.326) and color rendering index of 91.2. Overall, the characteristics of lanthanide ions endow the super performance of Cs2NaLnX6 NCs, which is obviously an important choice for future optoelectronic devices. [ABSTRACT FROM AUTHOR]

Active waveguides have attracted growing attention as a basic component of miniaturized and integrated photonic devices. However, most optical waveguide materials suffer from severe self‐absorption, which greatly increases the optical loss. Therefore, developing highly efficient red‐emitting materials with large Stokes shift and negligible self‐absorption is of great interest. Herein, this work proposes a strategy to achieve both large Stokes shifts and high photoluminescence quantum yield (PLQY) in organic metal halide via large cation engineering. Two zero‐dimensional antimony(III) chlorides, (TMA)2SbCl5 and (TMAA)2SbCl5, are designed and synthesized by screening the ligands with different cationic volumes. Experimental and theoretical results reveal that the large cation can promote the self‐trapped excitons emission and improve stability. Benefiting from the large Stokes shift (291 nm) and high PLQY (98.3%), the as‐prepared (TMAA)2SbCl5 microplate exhibits efficient active waveguide with low loss coefficient of 6.07 × 10−3 dB µm−1. This work not only develops a novel active waveguide material, but also provides insights into the role of organic cation, which will provide new inspiration for the exploitation of excellent luminescent metal halides and photonic devices. [ABSTRACT FROM AUTHOR]

Long afterglow luminescent materials have captured intense attention for their unique applications in biological imaging, photodynamic therapy, and optical anti‐counterfeiting. However, achieving highly efficient and tunable ultralong afterglow emission in all‐inorganic metal halides is an open challenge. Herein, Sb3+‐doped hexagonal CsCdCl3 metal halide is reported via hydrothermal reaction. Upon photoabsorption, the as‐synthesized compounds exhibit dual‐emission bands with a photoluminescence quantum yield (PLQY) of 59.6%, which can be attributed to the self‐trapped exciton emission out of the strong electron‐phonon coupling. After ceasing excitation of 365 nm, bright afterglow emission with the longest duration lasting up to 5000 s is witnessed in Sb3+‐doped CsCdCl3. More importantly, the color‐tunable and time‐dependent ultralong afterglow emission is realized via regulating the doping concentration of Sb3+, which should be due to the trap electrons increase gradually under high doping concentration. Given this unusual afterglow emission characteristics, the optical anti‐counterfeiting and information encryption are constructed based on as‐synthesized compounds. These findings not only help further understand the tunable afterglow emission mechanism in all‐inorganic metal halides, but also provide a new strategy for designing novel ultralong afterglow luminescent materials. [ABSTRACT FROM AUTHOR]

The optical properties of two-dimensional (2D) perovskites recently receive numerous research focus thanks to the strong quantum and dielectric confinement effects. In addition to the strong excitonic effect at room temperature, 2D perovskites also have appealing features that their optical properties can be flexibly tuned by alternating organic or inorganic layers. Particularly, 2D chiral perovskites and 2D perovskites based heterostructures are emerging as new platforms to extend their functionalities. To optimize performance of 2D perovskites-based optoelectronic devices, it is critical to understand the fundamentals and explore the strategies to engineer their optical properties. This review begins with an introduction to the excitons and self-trapped excitons of 2D perovskites. Subsequently, inorganic/organic layer effects on optical properties and 2D perovskites based heterostructures are discussed. We also discussed the nonlinear optical properties of 2D perovskite. We are looking forward to that this review can stimulate more efforts to understand and optimize the optical properties of 2D perovskites. [ABSTRACT FROM AUTHOR]