Efficient energy transfer from self-trapped excitons to Mn^(2+) dopants in CsCdCl_(3):Mn^(2+) perovskite nanocrystals

Mn^(2+)doping has been adopted as an efficient approach to regulating the luminescence properties of halide perovskite nano-crystals(NCs).However,it is still difficult to understand the interplay of Mn^(2+)luminescence and the matrix self-trapped exciton(STE)emission therein.In this study,Mn^(2+)-doped CsCdCl_(3) NCs are prepared by hot injection,in which CsCdCl_(3) is selected because of its unique crystal structure suitable for STE emission.The blue emission at 441 nm of undoped CsCdCl_(3) NCs originates from the defect states in the NCs.Mn^(2+)doping promotes lattice distortion of CsCdCl_(3) and generates bright orange-red light emission at 656 nm.The en-ergy transfer from the STEs of CsCdCl_(3) to the excited levels of the Mn^(2+)ion is confirmed to be a significant factor in achieving efficient luminescence in CsCdCl_(3):Mn^(2+)NCs.This work highlights the crucial role of energy transfer from STEs to Mn^(2+)dopants in Mn^(2+)-doped halide NCs and lays the groundwork for modifying the luminescence of other metal halide perovskite NCs.

Light emission from multiple self-trapped excitons in one-dimensional Ag-based ternary halides

Ternary metal halides based on Cu(I)and Ag(I)have attracted intensive attention in optoelectronic applications due to their excellent luminescent properties,low toxicity,and robust stability.While the self-trapped excitons(STEs)emission mechanisms of Cu(I)halides are well understood,the STEs in Ag(I)halides remain less thoroughly explored.This study explores the STE emission efficiency within the A_(2)AgX_(3)(A=Rb,Cs;X=Cl,Br,I)system by identifying three distinct STE states in each material and calculating their configuration coordinate diagrams.We find that the STE emission efficiency in this system is mainly determined by STE stability and influenced by self-trapping and quenching barriers.Moreover,we investigate the impact of structural compactness on emission efficiency and find that the excessive electron–phonon coupling in this system can be reduced by increasing the structural compactness.The atomic packing factor is identified as a low-cost and effective descriptor for predicting STE emission efficiency in both Cs_(2)AgX_(3) and Rb_(2)AgX_(3) systems.These findings can deepen our understanding of STE behavior in metal halide materials and offer valuable insights for the design of efficient STE luminescent materials.The datasets presented in this paper are openly available in Science Data Bank at https://doi.org/10.57760/sciencedb.12094.

Light-emitting diodes based on all-inorganic copper halide perovskite with self-trapped excitons

Light-emitting diodes based on lead halide perovskite have attracted great attention due to their outstanding performance.However,their application is plagued by the toxicity of Pb and the poor stability.Herein novel copper-based all inorganic perovskite CsCu2I3 with much enhanced stability has been reported with a potential photoluminescence quantum yield(PLQY)over 20%and self-trapped excitons(STE).By taking advantage of its extraordinary thermal stability,we successfully fabricate high-quality CsCu2I3 film through direct vacuum-based deposition(VBD)of CsCu2I3 powder.The resulting film shows almost the same PLQY with the synthesized powder,as well as excellent uniformity and stability.The perovskite light-emitting diodes(Pe-LED)based on the evaporated CsCu2I3 emitting layer achieve a luminescence of 10 cd/m2 and an external quantum efficiency(EQE)of 0.02%.To the best of our knowledge,this is the first CsCu2I3 Pe-LED fabricated by VBD with STE property,which offers a new avenue for lead-free Pe-LED.

Temperature-dependent self-trapped exciton emission in Cu(I) doped zinc-based metal halides from well-resolved excited state structures

Zero-dimensional metal halides are of unique structures and tunable photoluminescence properties,showing great potential applications such as light-emitting diodes(LEDs)and sensing.Herein,we successfully synthesized Cu^(+)doped(MA)_(2)ZnCl_(4)metal halides by a slow evaporation solvent method.The introduction of Cu^(+)results in sky-blue self-trapped exciton emission in(MA)_(2)ZnCl_(4) at 486 nm at room temperature,and a photoluminescence quantum yield is as high as 54.9%.Interestingly,at low temperatures,Cu^(+)-doped(MA)_(2)ZnCl_(4) exhibits two emission peaks located at 482 and 605 nm,respectively.This temperaturedependent dual emission indicates two excited state structures that exist on the triplet excited-state potential energy surface.In addition,the temperature sensor we fitted has good performance(Sr=1.65%·K^(−1)),which is the first attempt in Cu^(+) doped Znbased metal halides.Our work enriches the family of sky-blue metal halides and provides a promising strategy for building skyblue LEDs.

Doping suppresses lattice distortion of vacant quadruple perovskites to activate self-trapped excitons emission

The vacancy-ordered quadruple perovskite Cs_(4)CdBi_(2)Cl_(12),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 Cs_(4)CdBi_(2)Cl_(12) synthesized by hydrothermal method.Density functional theory calculations combined with experimental results evidence that the weak orange emission from Cs_(4)CdBi_(2)Cl_(12) 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 Cs_(4)CdBi_(2)Cl_(12),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 Cs_(4)CdBi_(2)Cl_(12):Ag^(+)reaches the maximum,about eight times that of the pristine sample.Moreover,the doped Cs_(4)CdBi_(2)Cl_(12) 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 I’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 Cs_(4)CdBi_(2)Cl_(12),highlighting its great potential as efficient emitter compatible for practical applications.

Origin of singlet self-trapped exciton and enhancement of photoluminescence quantum yield of organic–inorganic hybrid antimony(III)chlorides with the[SbCl_(5)]^(2)−units

Sb-based organic–inorganic hybrid metal halides(OIHMHs)with[SbCl5]2−units have been widely reported due to high photoluminescence quantum yield(PLQY)and occasional multiple self-trapped exciton(STE)emission bands mainly out of singlet and triplet states,and their multi-band emission is important in white light-emitting diode(WLED).However,not all these OIHMH compounds can produce both emissions out of singlet STE and triplet STE at room temperature simultaneously.It is crucial to consider how the singlet STE generates and retains to emit light at room temperature for this material’s design and application.Herein,a strategy is proposed that can significantly lift Sb halide PLQY by synthesizing two Sb-based OIHMHs using organic amine cations of different-sized and-quantity,which modulate the distance of neighboring emission centers.Therein,the occurrence of singlet STE emission is found to be closely related to the distance of[SbCl_(5)]^(2)−units and local unit distortion in the lattice.The larger distance can produce smaller local distortions,favoring the formation of the singlet STE emission band at higher energy.This is the first work to reveal the relationship between the local structure and the origin of the singlet STE emission band,providing new insights into the modulation of the Sb-based OIHMH’s emission.

Boosting self-trapped exciton emission from Cs_(3)Cu_(2)I_(5)nanocrystals by doping-enhanced exciton-phonon coupling

Self-trapped excitons(STEs)emission from halide perovskites with strong exciton-phonon coupling has attracted considerable attention due to the widespread application in optoelectronic devices.Nevertheless,the in-depth understanding of the relationship between exciton-phonon coupling and luminescence intensity remains incomplete.Herein,a doping-enhanced exciton-phonon coupling effect is observed in Cs_(3)Cu_(2)I_(5)nanocrystals(NCs),which leads to a remarkable increasement of their STEs emission efficiency.Mechanism study shows that the hetero-valent substitution of Cu+with alkaline-earth metal ions(AE^(2+))causes a greater degree of Jahn-Teller distortion between the ground state and excited state structures of[Cu_(2)I_(5)]_(3)-clusters as evidenced by our spectral analysis and first-principles calculations.As a consequence,an X-ray detector based on these Cs_(3)Cu_(2)I_(5):AE NCs delivers an X-ray imaging resolution of up to 10 lp·mm^(-1) and a low detection limit of 0.37μGyair·s^(-1),disclosing the potential of doping-enhanced exciton-phonon coupling effect in improving STEs-emission and practical application for X-ray imaging.

Self-trapped excitons in two-dimensional perovskites

With strong electron-phonon coupling,the self-trapped excitons are usually formed in materials,which leads to the local lattice distortion and localized excitons.The self-trapping strongly depends on the dimensionality of the materials.In the three dimensional case,there is a potential barrier for self-trapping,whereas no such barrier is present for quasi-one-dimensional systems.Two-dimensional(2D)systems are marginal cases with a much lower potential barrier or nonex istent potential barrier for the self-trapping,leading to the easier formation of self-trapped states.Self-trapped excitons emission exhibits a broadband emission with a large Stokes shift below the bandgap.2D perovskites are a class of layered structure material with unique optical properties and would find potential promising optoelectronic.In particular,self-trapped excitons are present in 2D per-ovskites and can significantly influence the optical and electrical properties of 2D perovskites due to the soft characteristic and strong electron-phonon interaction.Here,we summarized the luminescence characteristics,origins,and characterizations of self-trapped excitons in 2D perovskites and finally gave an introduction to their applications in optoelectronics.

Boosting triplet self-trapped exciton emission in Te(IV)-doped Cs_(2)SnCl_(6) perovskite variants

Perovskite variants have attracted wide interest because of the lead-free nature and strong self-trapped exciton (STE) emission. Divalent Sn(II) in CsSnX3 perovskites is easily oxidized to tetravalent Sn(IV), and the resulted Cs2SnCl6 vacancy-ordered perovskite variant exhibits poor photoluminescence property although it has a direct band gap. Controllable doping is an effective strategy to regulate the optical properties of Cs2SnX6. Herein, combining the first principles calculation and spectral analysis, we attempted to understand the luminescence mechanism of Te4+-doped Cs2SnCl6 lead-free perovskite variants. The chemical potential and defect formation energy are calculated to confirm theoretically the feasible substitutability of tetravalent Te4+ ions in Cs2SnCl6 lattices for the Sn-site. Through analysis of the absorption, emission/excitation, and time-resolved photoluminescence (PL) spectroscopy, the intense green-yellow emission in Te4+:Cs2SnCl6 was considered to originate from the triplet Te(IV) ion 3P1→1S0 STE recombination. Temperature-dependent PL spectra demonstrated the strong electron-phonon coupling that inducing an evident lattice distortion to produce STEs. We further calculated the electronic band structure and molecular orbital levels to reveal the underlying photophysical process. These results will shed light on the doping modulated luminescence properties in stable lead-free Cs2MX6 vacancy-ordered perovskite variants and be helpful to understand the optical properties and physical processes of doped perovskite variants.

Identifying self-trapped excitons in 2D perovskites by Raman spectroscopy[Invited]

Two-dimensional(2D)perovskites exhibit broadband emission due to strong exciton–phonon coupling-induced self-trapped excitons and thus would find important applications in the field of white-light emitting devices.However,the available identifying methods for self-trapped excitons are currently rather limited and complex.Here,we identify the existence of self-trapped excitons by Raman spectroscopy in both excited and non-excited states.Under excited states,the shifting of the Raman peak indicates the presence of the lattice distortion,which together with the extra Raman scattering peak reveals the presence of self-trapped excitons.Our work provides an alternative simple method to study self-trapped excitons in 2 D perovskites.

Self-trapped exciton emission in inorganic copper(Ⅰ)metal halides

The broad emission and high photoluminescence quantum yield of self-trapped exciton(STE)radiative recombination emitters make them an ideal solution for single-substrate,white,solid-state lighting sources.Unlike impurities and defects in semiconductors,the formation of STEs requires a lattice distortion,along with strong electron–phonon coupling,in low electrondimensional materials.The photoluminescence of inorganic copper(Ⅰ)metal halides with low electron-dimensionality has been found to be the result of STEs.These materials were of significant interest because of their leadfree,all-inorganic structures,and high luminous efficiencies.In this paper,we summarize the luminescence characteristics of zero-and one-dimensional inorganic copper(I)metal halides with STEs to provide an overview of future research opportunities.

Highly Efficient Self-Trapped Bluish White-Light Emission from[Pb4Cl5]3+Nodes in a Moisture-Tolerant Metal–Organic Framework

Highly luminescent zero-dimensional(0D)metal halide clusters attract widespread attention owing to strong exciton confinement and populated self-trapped states but often exhibit narrow emission and are susceptible to hydrolysis.Herein,we demonstrate a moisture-resistant metal–organic framework(MOF)consisting of cationic 0D[Pb_(4)Cl_(5)]^(3+)nodes bridged by adamantanetetracarboxylate.Upon near-UV excitation,the material emits intrinsic broadband bluish white-light emission with high external quantum efficiency of 35%and a color rendering index of 76.Unlike organoammonium cations in lead perovskites,the Pb-carboxylate coordination affords the MOF to be chemically stable and photostable in high humidity.The photoemitter exhibits undiminished photoemissions under ambient conditions[∼60%relative humidity(RH)]upon continuous UV irradiation(143 mW/cm^(2),365 nm)for 7 days.The insertion of[Na_(4)Cl]^(3+)moieties will connect 0D units into two-dimensional(2D)metal halide layers to limit structural strain and decrease the quantum efficiency from 35%to 15%,confirming the key importance of 0D units for efficient emission.

Charge self-trapping in two strand biomolecules:Adiabatic polaron approach

We investigate the properties of the excess charge(electron, hole) introduced into a two-strand biomolecule. We consider the possibility that the stable soliton excitation can be formed due to interaction of excess charge with the phonon subsystem. The influence of overlap of the molecular orbitals between adjacent structure elements of the macromolecular chain on the soliton properties is discussed. Special attention is paid to the influence of the overlapping of the molecular orbitals between structure elements placed on the different chains. Using the literature values of the basic energy parameters of the two-chain biomolecular structures, possible types of soliton solutions are discussed.

Temperature Effects on the Self-trapping Energy of a Polaron in a GaAs Parabolic Quantum Dot

The temperature and the size dependences of the self-trapping energy of a polaron in a GaAs parabolic quantum dot are investigated by the second order Rayleigh-Schrodinger perturbation method using the framework of the effective mass approximation. The numerical results show that the self-trapping energies of polaron in GaAs parabolic quantum dots shrink with the enhancement of temperature and the size of the quantum dot. The results also indicate that the temperature effect becomes obvious in small quantum dots

Cavity-Induced Self-Trapping of a Bose Josephson Junction

We investigate the self-trapping of a Bose Josephson junction, which is dispersively coupled to a driven optical cavity. The cavity-induced nonlinearity is presented analytically, and its effect results in the appearance of the self-trapping for the Bose-Einstein condensates in the Josephson oscillation regime. In addition, there exists competition between the nonlinearities induced by the interatomic interaction and by the driven cavity for the emergences of self-trapping. Our results show that the driven cavity can be utilized as a possible tool to produce the self-trapping for the condensates with weak interatomic interaction.

Localized self-trapping in two-dimensional molecular lattice with interaction between Wannier-Mott excitons and phonon lattice

We investigate the interactions of lattice pbonons with Wannier-Mott exciton, the exciton that has a large radius in two-dimensional molecular lattice, by the method of continuum limit approximation, and obtain that the self-trapping can also appear in two-dimensional molecular lattice with a harmonic and nonlinear potential. The exciton effect on molecular lattice does not distort the molecular lattice but only makes it localized and the localization can also react, again through phonon coupling, to trap the energy and prevents its dispersion.

Localized self-trapping in the two-dimensional discrete molecular lattice with the interaction between Frenkel excitons and phonons

We investigate the interactions of lattice phonons with Frenkel exciton, which has a small radius in a twodimensional discrete molecular lattice, by the virtue of the quasi-discreteness approximation and the method of multiplescale, and obtain that the self-trapping can also appear in the two-dimensional discrete molecular lattice with harmonic and nonlinear potential. The excitons＇ effect on the molecular lattice does not distort it but only causes it to localize which enables it to react again through phonon coupling to trap the energy and prevent its dispersion.

The effect of s-wave scattering length on self-trapping and tunneling phenomena of Fermi gases in one-dimensional accelerating optical lattices

We investigate the tunneling dynamics of the Fermi gases in an optical lattice in the Bose--Einstein condensation （BEC） regime. The three critical scattering lengths and the system energies are found in different cases of Josephson oscillation （JO）, oscillating-phase-type self-trapping （OPTST）, running-phase-type self-trapping （RPTST）, and self-trapping （ST）. It is found that the s-wave scattering lengths have a crucial role on the tunneling dynamics. By adjusting the scattering length in the adiabatic condition, the transition probability changes with the adiabatic periodicity and a rectangular periodic pattern emerges. The periodicity of the rectangular wave depends on the system parameters such as the periodicity of the adjustable parameter, the s-wave scattering length.

3-4 First-principles Investigation Self-trapping of Helium in Tungsten

The tungsten are deemed to be the most promising candidates as plasma facing material due to its high melting temperature, good thermal properties, low sputtering yields[1]. In the near surface of plasma facing materials high densities of interstitials and vacancies are produced in addition to high concentrations of hydrogen and helium (He). He easily are trapped by vacancies, dislocations, grain boundaries to form He bubble nucleation. When no traps are available, He spontaneously form clusters, which result in strong lattice strain. It can be relieved by ejecting one or more matrix atoms to form one or more Frenkel Pairs, i:e:vacancies and self-interstitial atoms. He cluster will be trapped by the vacancy it created, this is a self-trapping event[2].

Achieving Tunable Cold/Warm White‑Light Emission in a Single Perovskite Material with Near‑Unity Photoluminescence Quantum Yield

Single materials that exhibit efficient and stable white-light emission are highly desirable for lighting applications.This paper reports a novel zero-dimensional perovskite,Rb_(4)CdCl_(6):Sn^(2+),Mn^(2+),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 Sn^(2+)and Mn^(2+),cyan-orange dual-band emission with complementary spectral ranges is activated by the self-trapped excitons and d-d transitions of the Sn^(2+)and Mn^(2+)centers in the Rb_(4)CdCl_(6)host,respectively.Intriguingly,although Mn^(2+)ions doped in Rb_(4)CdCl_(6)are difficult to excite,efficient Mn^(2+)emission can be realized through an ultra-high-efficient energy transfer between Sn^(2+)and Mn^(2+)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 Sn^(2+)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 Sn^(2+)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.