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[Display omitted] • The lattice modification of Cs 2 NaInCl 6 was conducted by Ag and Zr dopants. • The emissive color temperature was tailored from warm- to cool-white with Zr content. • Double self-trapped excitons (STEs)-based pure-white afterglow was realized, which could last over 5 h. • 40 % of Zr dopants enhanced the initial afterglow intensity for ∼ 100-fold, compared with Cs 2 Na 0.9 Ag 0.1 InCl 6. • The bands of STEs were observed in steady-state absorption spectra thanks to energy storage. The incommensurable differences between the feeding and actual doping ratios of luminescent dopants and excessive reliance on rare-earth ions become two key problems in halide perovskite-based afterglow materials, restricting the production cost and further application. Here, we prepare a series of novel lead- and rare-earth-free halide afterglow phosphors Cs 2 (Na 0.9 Ag 0.1 In) 1- x Zr x Cl 6 under an ambient condition, in which the Zr dopants modify the lattice thus tailoring the emission spectrum and trap distribution, simultaneously. The focused Cs 2 (Na 0.9 Ag 0.1 In) 0.6 Zr 0.4 Cl 6 with mainly size distribution of ∼ 0.6–1.8 μm exhibits ∼ 350–850 nm ultrabroad white luminescence under ultra-violet excitation, and the introduced traps endow the white emission with a long-persistence of over 5 h after pre-irradiation. The absorption bands of self-trapped excitons (STEs) are observed in the steady-state absorption spectra during the afterglow process, suggesting the general accepted picosecond-scaled lifetimes of STEs have been successfully prolonged to hour-scale, which provide a potential opportunity for investigating the specific behavior of STEs. [ABSTRACT FROM AUTHOR]

Excitonic effects in 1D semiconductors can be qualitatively different from those in higher dimensions. In particular, the Sommerfeld factor, the ratio of the above-band-edge excitonic continuum absorption to free electron-hole pair generation, has been shown to be less than 1 (suppressed) in 1D systems while it is larger than 1 (enhanced) in 2D and 3D systems. Strong continuum suppression indeed exists in semiconducting single-wall carbon nanotubes, a prototypical 1D semiconductor. However, absorption spectra for carbon nanotubes are typically fit with a combination of Lorentzians and a polynomial background baseline with little physical meaning. Here, we performed absorption measurements in aligned single-chirality (6,5) carbon nanotube films. The obtained spectra were fit with our theoretical model obtained by solving the Boltzmann scattering equation involving fifty-nine different types of transitions among three different types of quasiparticles. Specifically, we took into account microscopic interactions between photons, phonons, and excitons, including their dispersions, which unambiguously demonstrated that the background absorption is due to phonon-assisted transitions from the semiconductor vacuum to finite-momentum continuum states of excitons. The excellent agreement we obtained between experiment and theory suggests that our numerical technique can be seamlessly extended to compute strongly out-of-equilibrium many-body dynamics and time-resolved spectra in low-dimensional materials. [Display omitted] [ABSTRACT FROM AUTHOR]

Ce+3 doped CsLaSiS 4 single crystals were synthesized using high-temperature flux synthesis. XRD analysis showed that the products are isostructural to CsLaSiS 4 and crystallize in orthorhombic space group Pnma. Absorption spectra were studied at room temperature, and photoluminescence properties were examined in the temperature range of 5–310 K. The energy of interband transitions E g = 3.75 eV was determined at room temperature in the Tauc model. At room temperature, only a non-elementary d → f emission band of Ce+3 ions was observed in the 520 nm region. The luminescence kinetics upon excitation by a pulsed cathode beam or X-ray synchrotron radiation exhibited a dominant nanosecond component. Decay time, as well as build-up time, decreased with increasing concentration of Ce+3 ions. Concentration quenching of Ce+3 emission was not observed up to 11.9 mol% of Ce+3 ions. At a low temperature of 5 K, new wide emission bands at 422 and 688 nm appeared in the photoluminescence spectrum. It is shown that the 422 nm band in the photoluminescence spectrum corresponds to host emission, specifically the luminescence of self-trapped excitons (STE). The 688 nm emission band corresponds to defect-related luminescence. STE emission is quenched according to the Mott law at temperatures above 26 K with an activation energy of 20 meV. An efficient energy transfer channel from the STE to the Ce+3 ion via the radiative resonance mechanism is observed. The emission of Ce+3 ions and defect-related luminescence can be excited by the intracenter way, due to electron-hole recombination, or by the creation of defect bound excitons. Based on the obtained spectroscopic data, a band scheme illustrating the processes of relaxation of electronic excitations at T = 5 K in Ce+3 doped CsLaSiS 4 crystals is proposed. [Display omitted] • Ce+3 doped CsLaSiS 4 single crystals were obtained through high-temperature flux synthesis. • Inter configurational d-f transitions in Ce3+ ions were studied upon both UV- and X-ray excitation. • Luminescence kinetic studies were conducted using a pulsed cathode beam and X-ray synchrotron radiation. • Self-trapped excitons, defect-bound excitons, and impurity luminescence were observed at T = 5 K. [ABSTRACT FROM AUTHOR]

The exciton states in the single-walled carbon nanotubes (SWNTs) with Stone–Wales (SW) defects are theoretically studied in the tight-binding model. It is found that for the semiconducting zigzag tubes (10, 0) with different concentration of SW defect, the exciton energies move to low energy region with increasing the concentration of SW defect, and the symmetry broken by the SW defects leads to splitting of the degenerate exciton energy levels, which can be seen clearly from the linear absorption spectra of defected SWNTs. As detected from the linear absorption spectra, we can give some information on the concentration of the SW defect existing in the SWNTs. [ABSTRACT FROM AUTHOR]

• Optical properties of monoclinic SbI3 are investigated using DFT calculations and experiment. • The calculated absorption spectra of six (hkl) planes show highly anisotropic nature. • 2.66 eV or 2.7 eV are possible indirect band gaps from band structure compared to measured 2.8 eV. • One exciton appears at 3.56 eV for (hkl) oriented film and two excitons at 2.95 eV and 3.30 eV for (1 3 0) • The experimental and theoretical optical properties match reasonably well. Structurally characterized antimony triiodide films grown by vacuum thermal evaporation exhibit anisotropic exciton formation at room temperature for different (hkl) oriented growth. Band structure of monoclinic SbI 3 was calculated using Density functional Theory with appropriate functional along with the absorption spectra of different (hkl) planes for comparing with the experimental results. The indirect band gap of 2.8 eV determined by measured absorption spectra matches closely with the calculated 2.66 eV. All (hkl) oriented films show one exciton at 3.56 eV which can be interpreted as direct type along D symmetry from the band structure. Similarly, the two excitons at 2.95 eV and 3.30 eV appearing for (1 3 0) oriented films can also be direct either at D or B symmetry. All three excitonic transitions are found to be from Iodine p states to Antimony p states. [ABSTRACT FROM AUTHOR]

All-inorganic lead halide perovskites nanocrystals (NCs) have been demonstrated to be promising candidates for optoelectronic devices, but preparing perovskite NCs with high photoluminescence quantum yields (PLQYs) and excellent stability has been a challenge. In this work, CsPbBr 3 /Cs 4 PbBr 6 core/shell NCs with a PLQYs of 87.23% and long-term stability in ambient environments was prepared by room temperature inverse microemulsion method. The excellent stability of the sample was attributed to the protection of Cs 4 PbBr 6 , and higher PLQYs could be owing to the passivation effect of the core/shell structure. To illustrate the distribution of photogenerated carrier in the core/shell structure, a confined excitons model was proposed based on time-resolved PL and temperature dependent PL measurements. Femtosecond time-resolved transient absorption spectra measurements were performed upon different excitation wavelength to unveil the photogenerated carrier dynamics in core/shell NCs. Upon 300 nm excitation, a carrier transfer process with the time of 3.18 ps from shell to core layer was observed. Furthermore, both two- and three-photon absorption PL was discovered in core/shell NCs, further verifying the carrier transfer process. [Display omitted] • Fabrication of strongly luminescent and highly stable CsPbBr 3 /Cs 4 PbBr 6 core/shell NCs. • A confined excitons model proposed for illustrating the higher PLQY in core/shell NCs. • A carrier transfer process from shell to core layer was observed in core/shell NCs. • Multi-photon absorption PL was observed further verifying the carrier transfer process. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fluorescence Resonance Energy Transfer from P3HT to CuInSe 2. • Analytical study of the absorption and emission spectra of P3HT:CuInSe 2 composites. • Förster distance of critical energy transfer is estimated as 3.61 nm. • The average distance between donor–acceptor is found to be 4.71 nm. • Analysis of resonance charge transfer by estimation of HOMO-LUMO energy of donor–acceptor. This letter reports the paramount fluorescence resonance energy transfer mechanism for photo induced charge transfer from P3HT to solvothermally derived CuInSe 2. The HOMO (-4.85 eV) and LUMO (-3.38 eV) energy states of CuInSe 2 (electrical conductivity = 1.1x 10-7 Scm−1) are determined from cyclic voltammetry and optical study. This HOMO-LUMO position agrees to select P3HT polymer as possible donor of excitons. Steady-state luminescence study of composite (P3HT:CuInSe 2) demonstrates possibility of successful charge transfer. Stern–Volmer analysis of absorption and emission spectroscopy ensures static energy quenching phenomena. The Förster distance (R 0) of critical energy transfer is estimated as 3.61 nm. The average distance between donor–acceptor (r avg = 4.71 nm) is<8 nm and within the range 0.5R 0 < r < 1.5R 0 (1.81 nm < r < 5.42 nm), which ensures energy transfer from P3HT to CuInSe 2. [ABSTRACT FROM AUTHOR]

Blue and green light emitting CsPbBr 3 and CsPb(Cl/Br) 3 perovskite quantum dots glasses (QDGs) have been fabricated in multi-component borate glass matrices by melt quenching method and following heat treatment. Absorption spectra show regular blue shift of first exciton absorption peak from CsPbBr 3 to CsPb(Cl/Br) 3 QDGs. Photoluminescence spectra show that CsPbBr 3 and CsPb(Cl/Br) 3 QDGs have adjustable emission in the wavelengths from 528 to 442 nm. The full width at half maximum (FWHM) is 15–17 nm and 21–31 nm for CsPbBr 3 and CsPb(Cl/Br) 3 QDGs respectively. Emission map and photoluminescence excitation spectra show broad band excitation characteristics of the exciton emission. Photoluminescence decay shows bi-exponential function for both CsPbBr 3 and CsPb(Cl/Br) 3 QDGs. As the ratio of Cl/Br increases from CsPbBr 3 to CsPb(Cl/Br) 3 QDGs, the short and long lifetime components roughly decrease from 9.7 to 4.0 ns and from 87.8 to 55.2 ns respectively, and the average lifetime decreases from 72.2 to 36.5 ns. Photoluminescence quantum yield changes from 82.8% to 5.7%. Temperature dependence of PL spectra in the range of 28–120 °C shows that integrated intensity obviously decreases with increasing temperature, but the emission peak wavelength and FWHM almost do not change. • Absorption spectra show blue-shift for CsPbBr 3 and CsPb(Cl/Br) 3 QDGs with different Cl/Br ratios. • Photoluminescence spectra show blue shift from 528 to 442 nm for CsPbBr 3 and CsPb(Cl/Br) 3 QDGs. • Narrow FWHM is 15–17 nm and 21–31 nm for CsPbBr 3 and CsPb(Cl/Br) 3 QDGs respectively. • With increasing Cl/Br ratio, short lifetime component and PLQY decrease with the same rule. • With increasing temperature, integrated intensity decreases, but emission peak and FWHM do not change. [ABSTRACT FROM AUTHOR]