Exciton emissions of CdS nanowire array fabricated on Cd foil by the solvothermal method

Nanowires have recently attracted more attention because of their low-dimensional structure, tunable optical and electrical properties for next-generation nanoscale optoelectronic devices. Cd S nanowire array, which is(002)-orientation growth and approximately perpendicular to Cd foil substrate, has been fabricated by the solvothermal method. In the temperature-dependent photoluminescence, from short wavelength to long wavelength, four peaks can be ascribed to the emissions from the bandgap, the transition from the holes being bound to the donors or the electrons being bound to the acceptors, the transition from Cd interstitials to Cd vacancies, and the transition from S vacancies to the valence band,respectively. In the photoluminescence of 10 K, the emission originated from the bandgap appears in the form of multiple peaks. Two stronger peaks and five weaker peaks can be observed. The energy differences of the adjacent peaks are close to 38 me V, which is ascribed to the LO phonon energy of Cd S. For the multiple peaks of bandgap emission, from low energy to high energy, the first, second, and third peaks are contributed to the third-order, second-order, and first-order phonon replica of the free exciton A, respectively;the fourth peak is originated from the free exciton A;the fifth peak is contributed to the first-order phonon replica of the excitons bound to neutral donors;the sixth and seventh peaks are originated from the excitons bound to neutral donors and the light polarization parallel to the c axis of hexagonal Cd S, respectively.

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.

Antimony-Doping Induced Highly Efficient Warm-White Emission in Indium-Based Zero-Dimensional Perovskites

Indium(In)-based halide perovskites are desirable for next-generation phosphors and emitting devices,due to their broad emission,nontoxicity,and oxidization avoidance capabilities.However,the In-based perovskites always exhibit low external photoluminescence quantum efficiency(PLQE)as a result of their weak light absorption near the corresponding excitation region,and thus,are limited in extended applications.Herein,we have developed an antimony(Sb)-doping strategy to improve the absorption ability of Cs2InCl5·H2O in the ultraviolet region.Excitingly,we obtained a warm-light phosphor with ultrahigh external(internal)PLQE of 72.8%(86.7%).Typically,upon 1.5%Sb doping,the single-crystalline Cs2InCl5·H2O perovskite displayed a stronger warm-light emission at∼610 nm with a large Stokes shift of 295 nm and full width at half maximum(FWHM)of 164 nm.Density functional theory(DFT)calculations revealed that the Sb-doping induced an impurity level in the bandgap,increasing the density of state(DOS),and promoted more carriers into the conduction band maximum.Furthermore,external PLQE from 18%to 59%could be realized in other zero-dimensional In-based perovskites through the same doping strategy.

Methanol-induced luminescence vapochromism based on a Sb^(3+)-doped organic indium halide hybrid

Ion doping has been demonstrated as a practical approach to achieving highly efficient luminescence in both inorganic phosphors and organic-inorganic hybrids.The asformed doping species show great potential in optoelectronic applications due to their high photoluminescence quantum yield(PLQY)and excellent stability.Herein,we report highly emissive Sb^(3+)-doped indium halides(C_(6)H_(18)N_(2))InCl_(5)·H_(2)O:Sb(C_(6)H_(18)N_(2)^(2+)=N,N,N',N'-tetramethylethane-1,2-diammonium)prepared by solution evaporation methods with an emission that peaked at 565 nm and a PLQY of 74.6%.Photophysical characterizations and density functional theory computational studies verify the broadband emission originating from a self-trapped exciton.Interestingly,a drastic red shift of the emission peak from 565 to 663 nm with yellow luminescence turning to red is observed once the(C_(6)H_(18)N_(2))InCl_(5)·H_(2)O:Sb hybrid is exposed to methanol vapor.Moreover,when the methanol-exposed hybrid is put in air,the emission reverts to 565 nm in several minutes.Single-crystal X-ray diffraction studies show a subsequent structure distortion upon the coordination of methanol to the Sb(III)center,which is responsible for the drastic red shift of the emission.Encouragingly,we found that(C_(6)H_(18)N_(2))InCl_(5)·H_(2)O:Sb exhibits a specific response to methanol vapor after screening a series of volatile organic compounds with different polarities.Besides,a negligible change of the emission intensity is observed after several cycles of uptaking and releasing methanol.The high fatigue resistance and specific solvent response of the Sb^(3+)-doped indium halide make it a very promising methanol detector.