Temperature-dependent photoluminescence of lead-free cesium tin halide perovskite microplates

Tin halide perovskites recently have attracted extensive research attention due to their similar electronic and band structures but non-toxicity compared with their lead analogues. In this work, we prepare high-quality CsSnX_(3)(X=Br,I) microplates with lateral sizes of around 1–4 μm by chemical vapor deposition and investigate their low-temperature photoluminescence(PL) properties. A remarkable splitting of PL peaks of the CsSnBr_(3)microplate is observed at low temperatures. Besides the possible structural phase transition at below 70 K, the multi-peak fittings using Gauss functions and the power-dependent saturation phenomenon suggest that the PL could also be influenced by the conversion from the emission of bound excitons into free excitons. With the increase of temperature, the peak position shows a blueshift tendency for CsSnI_(3), which is governed by thermal expansion. However, the peak position of the CsSnBr3microplate exhibits a transition from redshift to blueshift at ~160 K. The full width at half maximum of CsSnX_(3)broadens with increasing temperature, and the fitting results imply that longitudinal optical phonons dominate the electron–phonon coupling and the coupling strength is much more robust in CsSnBr3than in CsSnI_(3). The PL intensity of CsSnX_(3)microplates is suppressed due to the enhanced non-radiative relaxation and exciton dissociation competing with radiative recombination. According to the Arrhenius law, the exciton binding energy of CsSnBr_(3)is ~38.4 meV, slightly smaller than that of CsSnI_(3).

Temperature-dependent photoluminescence of size-tunable ZnAgInSe quaternary quantum dots

Colloidal ZnAgInSe(ZAISe) quantum dots(QDs) with different particle sizes were obtained by accommodating the reaction time. In the previous research, photoluminescence(PL) of ZAISe QDs only could be tuned by changing the composition. In this work the size-tunable photoluminescence was observed successfully. The red shift in the photoluminescence spectra was caused by the quantum confinement effect. The time-resolved photoluminescence indicated that the luminescence mechanisms of the ZAISe QDs were contributed by three recombination processes. Furthermore, the temperature-dependent PL spectra were investigated. We verified the regular change of temperature-dependent PL intensity, peak energy, and the emission linewidth of broadening for ZAISe QDs. According to these fitting data, the activation energy(?E) of ZAISe QDs with different nanocrystal sizes was obtained and the stability of luminescence was discussed.

Temperature-dependent photoluminescence spectra of GaN epitaxial layer grown on Si(111) substrate

In this paper, the temperature-dependent photoluminescence(PL) properties of Ga N grown on Si(111) substrate are studied. The main emission peaks of Ga N films grown on Si(111) are investigated and compared with those grown on sapphire substrates. The positions of free and bound exciton luminescence peaks, i.e., FX A and D0 X peaks, of Ga N films grown on Si(111) substrates undergo red shifts compared with those grown on sapphire. This is attributed to the fact that the Ga N films grown on sapphire are under the action of compressive stress, while those grown on Si(111) substrate are subjected to tensile stress. Furthermore, the positions of these peaks may be additionally shifted due to different stress conditions in the real sample growth. The emission peaks due to stacking faults are found in Ga N films grown on Si(111) and an S-shaped temperature dependence of PL spectra can be observed, owing to the influence of the quantum well(QW) emission by the localized states near the conduction band gap edge and the temperature-dependent distribution of the photo-generated carriers.

Temperature-dependent photoluminescence of highly luminescent water-soluble CdTe quantum dots

高度光的水溶性的 CdTe 量点(QD ) 与一位 electrogener ated 先锋被综合了。获得的 CdTe QD 能拥有好可结晶性，高量收益(QY ) 和有利稳定性。而且，一个察觉系统为 QD 的温度依赖者 PL 的调查第一被设计。

Optical properties of InGaAsBi/GaAs strained quantum wells studied by temperature-dependent photoluminescence

The effect of bismuth on the optical properties of InGaAsBi/GaAs quantum well structures is investigated using the temperature-dependent photoluminescence from 12 K to 450 K.The incorporation of bismuth in the InGaAsBi quantum well is confirmed and found to result in a red shift of photoluminescence wavelength of 27.3 meV at 300 K.The photoluminescence intensity is significantly enhanced by about 50 times at 12 K with respect to that of the InGaAs quantum well due to the surfactant effect of bismuth.The temperature-dependent integrated photoluminescence intensities of the two samples reveal different behaviors related to various non-radiative recombination processes.The incorporation of bismuth also induces alloy non-uniformity in the quantum well,leading to an increased photoluminescence linewidth.

Temperature-dependent photoluminescence on organic inorganic metal halide perovskite CH3NH3Pb I3-xClx prepared on ZnO/FTO substrates using a two-step method

Temperature-dependent photoluminescence characteristics of organic-inorganic halide perovskite CH_3NH_3Pb I_(3-x)Cl_x films prepared using a two-step method on ZnO/FTO substrates were investigated. Surface morphology and absorption characteristics of the films were also studied. Scanning electron microscopy revealed large crystals and substrate coverage. The orthorhombic-to-tetragonal phase transition temperature was^140 K. The films' exciton binding energy was 77.6 ± 10.9 meV and the energy of optical phonons was 38.8 ± 2.5 meV. These results suggest that perovskite CH_3NH_3Pb I_(3-x)Cl_x films have excellent optoelectronic characteristics which further suggests their potential usage in perovskitebased optoelectronic devices.

Fabrication and temperature-dependent photoluminescence spectra of Zn–Cu–In–S quaternary nanocrystals

A series of Zn–Cu–In–S nanocrystals(ZCIS NCs) are prepared and the optical properties of the ZCIS NCs are tuned by adjusting the reaction time. It is interesting to observe that the temperature-dependent photoluminescence(PL) spectra of the ZCIS NCs show a redshift with decreasing intensity at low temperature(50–280 K) and a blueshift at high temperature(318–403 K). The blueshift can be explained by the thermally active phonon-assisted tunneling from the excited states of the low-energy emission band to the excited states of the high-energy emission band.

Anomalous temperature-dependent photoluminescence peak energy in InAlN alloys

InAlN has been studied by means of temperature-dependent time-integrated photoluminescence and time-resolved photoluminescence.The variation of PL peak energy did not follow the behavior predicted by Varshni formula, and a faster redshift with increasing temperature was observed. We used a model that took account of the thermal activation and thermal transfer of localized excitons to describe and explain the observed behavior. A good fitting to the experiment result is obtained. We believe the anomalous temperature dependence of PL peak energy shift can be attributed to the temperature-dependent redistribution of localized excitons induced by thermal activation and thermal transfer in the strongly localized states. V-shaped defects are thought to be a major factor causing the strong localized states in our In_(0.153) Al_(0.847) N sample.

Ostensibly perpetual optical data storage in glass with ultra-high stability and tailored photoluminescence

Long-term optical data storage(ODS)technology is essential to break the bottleneck of high energy consumption for information storage in the current era of big data.Here,ODS with an ultralong lifetime of 2×10^(7)years is attained with single ultrafast laser pulse induced reduction of Eu^(3+)ions and tailoring of optical properties inside the Eu-doped aluminosilicate glasses.We demonstrate that the induced local modifications in the glass can stand against the temperature of up to 970 K and strong ultraviolet light irradiation with the power density of 100 kW/cm^(2).Furthermore,the active ions of Eu^(2+)exhibit strong and broadband emission with the full width at half maximum reaching 190 nm,and the photoluminescence(PL)is flexibly tunable in the whole visible region by regulating the alkaline earth metal ions in the glasses.The developed technology and materials will be of great significance in photonic applications such as long-term ODS.

Photoluminescence Enhancement of Aluminum Ion Intercalated MoS_(2)Quantum Dots

Low photolumines-cence(PL)quantum yield of molybdenum disulfide(MoS_(2))quan-tum dots(QDs)has lim-ited practical applica-tion as potential fluores-cent materials.Here,we report the intercalation of aluminum ion(Al^(3+))to enhance the PL of MoS_(2)QDs and the un-derlying mechanism.With detailed characterization and exciton dynamics study,we suggest that additional surface states including new emission centers have been effectively introduced to MoS_(2)QDs by the Al^(3+)intercalation.The synergy of new radiative pathway for exciton re-combination and the passivation of non-radiative surface traps is responsible for the en-hanced fluorescence of MoS_(2)QDs.Our findings demonstrate an efficient strategy to improve the optical properties of MoS_(2)QDs and are important for understanding the regulation effect of surface states on the emission of two dimensional sulfide QDs.

Anomalous photoluminescence enhancement and resonance charge transfer in type-II 2D lateral heterostructures

Type-Ⅱband alignment can realize the efficient charge transfer and separation at the semiconductor heterointerface,which results in photoluminescence(PL)quenching.Recently,several researches demonstrated great enhancement of localized PL at the interface of type-Ⅱtwo-dimensional(2D)heterostructure.However,the dominant physical mechanism of this enhanced PL emission has not been well understood.In this work,we symmetrically study the exciton dynamics of type-Ⅱlateral heterostructures of monolayer MoS_(2) and WS_(2) at room temperatures.The strong PL enhancement along the one-dimensional(1D)heterointerface is associated with the trion emission of the WS_(2) shell,while a dramatic PL quenching of neutral exciton is observed on the MoS_(2) core.The enhanced quantum yield of WS2trion emission can be explained by charge-transfer-enhanced photoexcited carrier dynamics,which is facilitated by resonance hole transfer from MoS_(2) side to WS_(2) side.This work sheds light on the 1D exciton photophysics in lateral heterostructures,which has the potential to lead to new concepts and applications of optoelectronic device.

Thermally enhanced photoluminescence and temperature sensing properties of Sc2W3O12:Eu3+ phosphors

Recently, lanthanide-ion-doped luminescent materials have been extensively used as optical thermometry probes due to their fast responses, non-contact, and high sensitivity properties. Based on different responses of two emissions to temperature, the fluorescence intensity ratio(FIR) technique can be used to estimate the sensitivities for assessing the optical thermometry performances. In this study, we introduce different doping concentrations of Eu^(3+) ions into negative thermal expansion material Sc2W3O12to increase the thermal-enhanced luminescence from 373 K to 548 K, and investigate the temperature sensing properties in detail. All samples can exhibit their good luminescence behaviors thermally enhanced.The emission intensity of Sc2W3O12:6-mol% Eu3+phosphor reaches 147.8% of initial intensity at 473 K. As the Eu3+doping concentration increases, the resistance of the sample to thermal quenching decreases. The FIR technique based on each of the transitions 5D→7F_(1)(592 nm) and 5D→7F_(2)(613 nm) of Eu3+ions demonstrates a maximum relative temperature sensitivity of 3.063% K-1at 298 K for Sc_(2)W_(3)O_(12):6-mol% Eu3+phosphor. The sensitivity of sample decreases with the increase of Eu3+concentration. Benefiting from the thermal-enhanced luminescence performance and good temperature sensing properties, the Sc_(2)W_(3)O_(12):Eu^(3+)phosphors can be used as optical thermometers.

Thickness Dependent Behavior of Photoluminescence of Tris(8-hydroxyquinoline)Aluminum Film

通过原位测量对八-羟基喹啉铝薄膜(Alq_3)光致发光的厚度依赖性质进行了研究.在 Alq_3向玻璃衬底沉积的初始阶段,Alq_3光致发光谱峰发生了显著红移,此后谱峰随着 Alq_3厚度的增加红移变缓并趋于饱和.Alq_3薄膜厚度从2nm 逐渐变化到500nm 时,Alq_3谱峰位总红移约为12nm.这种 Alq_3薄膜沉积的初始阶段 Alq_3谱峰的显著红移可归因于二维激子向三维激子态的转变.同时,由于激子同衬底的相互作用所引起的非辐射衰变,在 Alq_3沉积的初始阶段 Alq_3光致发光谱峰的强度呈现不同的变化,随后该谱峰的强度随 Alq_3薄膜厚度的增加而快速增加,并在薄膜厚度较大时,趋向于饱和.

Preparation, Structure, Photoluminescence and Energy Transfer Mechanism of a Novel Holmium Complex

A novel holmium complex [Ho(HIA)_2(H_2O)_4(NO_3)](NO_3)_2(1, HIA = isonicotinic acid) has been synthesized through hydrothermal reactions and characterized by single-crystal X-ray diffraction. Complex 1 crystallizes in the C2/c space group of monoclinic system: a = 14.4797(7), b = 12.4768(2), c = 13.3471(5) ?, β = 118.690(4)°, V = 2115.26(13) ?~3, C_(12)H_(16)HoN_5O_(17), Mr = 667.23, Z = 4, Dc = 2.095 g/cm^3, μ(Mo Kα) = 3.838 mm^(–1) and F(000) = 1304. The crystal structure of 1 is characterized by an isolated structure. Solid-state photoluminescence experiment uncovers that it shows yellow light emission. The emission bands are originated from the characteristic emission of the 4 f electrons intrashell transition of the ~5S_2 → ~5I_8 and ~5F_5 → ~5I_8 of the Ho^(3+) ions. Energy transfer mechanism is explained by the energy level diagram of the Ho3+ ion and the isonicotinic acid ligand. It has remarkable CIE chromaticity coordinates of(0.4929, 0.4632), so it may be a promising color converter for lighting and displays.

Upconversion Photoluminescence and Energy Transfer Mechanism of a Novel Terbium-mercury Compound

A novel terbium-mercury complex [Tb(IA)3(H3 O)2]2 n(2 n HgCl4)(n Hg2 Cl5)·n H3 O· 3 n H2 O(1, HIA = isonicotinic acid) has been synthesized through hydrothermal reactions and characterized by single-crystal X-ray diffraction. Complex 1 crystallizes in the C2/c space group of monoclinic system with a = 24.2347(5), b = 20.8342(6), c = 15.3206(3) ?, β = 128.257(2)°, V = 6074.3(2) ?3, C36H41Cl13Hg4N6O20Tb2, Mr = 2458.80, Z = 4, Dc = 2.689 g/cm3, μ(Mo Kα) = 13.014 mm–1 and F(000) = 4520. The crystal structure of 1 is characterized by a one-dimensional(1-D) chain-like structure. Solid-state UV/Vis diffuse reflectance spectrum reveals the existence of a wide optical band gap of 3.36 eV. Solid-state photoluminescence experiment uncovers that it shows reddish brown upconversion emission. The emission bands are originated from the characteristic emission of the 4 f electrons intrashell transition of the 5D4 → 7 FJ(J = 6, 5, 4) of the Tb3+ ions. Energy transfer mechanism is explained by the energy level diagram of the Tb3+ ion and the isonicotinic acid ligand. It shows a remarkable CIE chromaticity coordinates(0.4158, 0.4005).

Photoluminescence Properties of Porous Silicon Based on FZ(H) Si Wafer

The photoluminescence (PL) properties of porous silicon (PS) have been studied based on n-type single- crystal (111) silicon wafers (80-90Ω .cm in the resistivity). The porous silicon layers (PSL) were created by anodizing the wafers with a denuded zone of 20-40 μm formed by neutron transmutation doping (NTD) and thermal treatment at 940℃ for 4 h and then 700℃ for 2 h, two-step heating of the floating-zone silicon (FZ Si) grown in a hydrogen (H2) ambience. By surface modification with stannic chloride or amine immersion and rapid thermal oxidation (RTO), the PL peak position from the PS can be qualitatively controlled factitiously. The as-prepared PS shows an orange-yellow luminescence, while the modified samples emit red, green and blue luminescence. Mechanisms for the different colors of the PL are discussed. Fourier transform infrared (FTIR) is carried out to analyze the differences in the structural configuration of the PS samples.

Red Electroluminescence and Photoluminescence from Novel Binuclear Europium Complex with Squaric Acid Ligand

A novel binuclear europium b-diketone complex with squaric acid ligand was synthesized for the first time. Its structure was elucidated by IR, UV, and Elemental Analysis. Red light emitting diode (LED) was fabricated by using the novel europium complex as an emitting layer, tris(8-quinolinolate) aluminum (III) (Alq3) as an electron-transporting layer, N, N’-diphenyl-N, N’-(3-methylphenyl)-1,1’-biphenyl-4,4’-diamine (TPD) as a hole-transporting layer. A cell structure of indium-tin-oxide/TPD/Eu-complex/Alq3/Mg: Ag was employed. Red electroluminescence was observed at room temperature with dc bias voltage of 2 V in this cell. Red emission peaks at about 613 nm with maximum luminance of over 106 cd/m2. Compared with the EL luminance from those europium complexes reported before, one from the Eu-complex is best in the same cells.

Photoluminescence of rare-earth ion(Eu^(3+), Tm^(3+), and Er^(3+))-doped and co-doped ZnNb_2O_6 for solar cells

Visible converted emissions produced at an excitation of 286 nm in Zn Nb2O6 ceramics doped with rare-earth ions(RE= Eu3+, Tm3+, Er3+or a combination of these ions) were investigated with the aim of increasing the photovoltaic efficiency of solar cells. The structure of RE:Zn Nb2O6 ceramics was confirmed by x-ray diffraction patterns. The undoped Zn Nb2O6 could emit a blue emission under 286-nm excitation, which is attributed to the self-trapped excitons' recombination of the efficient luminescence centers of edge-shared Nb O6 groups. Upon 286-nm excitation, Eu:Zn Nb2O6, Tm:Zn Nb2O6, and Er:Zn Nb2O6 ceramics showed blue, green, and red emissions, which correspond to the transitions of5D0→7FJ(J = 1–4)(Eu3+),1G4→3H6(Tm3+), and2H11/2/4S3/2→4I15/2(Er3+), respectively. The calculated CIE chromaticity coordinates of Eu:Zn Nb2O6, Tm:Zn Nb2O6, and Er:Zn Nb2O6are(0.50, 0.31),(0.14, 0.19), and(0.29, 0.56), respectively. RE ionco-doped Zn Nb2O6 showed a combination of characteristic emissions. The chromaticity coordinates of Eu/Tm:Zn Nb2O6,Eu/Er:Zn Nb2O6, and Tm/Er:ZnNb2O6 were calculated to be(0.29, 0.24),(0.45, 0.37), and(0.17, 0.25).

Sol-gel Synthesis and Photoluminescence of InP Nanocrystals Embedded in Silica Glasses

III-Vsemiconductor nanocrystals rarely exist as spherical inclusions inside glasses, due to difficulties during their preparation, such as high toxic reagents or fast oxidation under usual glass technology temperatures. In this article a sol-gel method for synthesis of InP nanocrystals embedded in silica glasses was described. Gels were synthesized by hydrolysis of a complex solution of Si(OC 2 H 5 ) 4 , InCl 3 4H 2 O and PO(OC 2 H 5 ) 3 . Then, the gels were heated at 600 o C in the presence of H 2 gas to form fine cubic InP crystallites. Raman spectrum showed InP longitudinal-optic mode (342cm -1 ) and transverse-optic mode (303cm -1 ). The size of InP nanocrystals was found to be from 2 to 8 nm in diameter by transmission electron microscopy. A strong photoluminescence with peaks at, 606, 730nm 856 nm was observed from 3InP/100SiO 2 nanocompositions. The temperature-and excitation power-dependent PL spectra from the nanocomposition are measured in order to confirm the origin of the PL spectra. These behaviors of the three peaks emissions suggest that 606, 733, and 856 nm emissions do not have the same origin. The PL with peak at 856nm arise from the cubic InP nanocrystallites embedded in the SiO 2 gel glasses. The 605 and 732 nm emissions may arise from the SiO 2 gel glass matrix or the interface between the InP crystallite core and SiO2 glass matrix.

Two Cd(Ⅱ) Coordination Polymers Based on a Flexible Tricarboxylate Ligand: Syntheses, Structures, and Photoluminescence and Catalytic Properties

Studies on the synthesis and design of coordination polymers(CPs) with flexible ligands are of great interest owing to their dynamic structures and promising applications. The title coordination polymers, {[Cd·(HTTTA)·(phen)]·2H_2 O}n(1) and [Cd·(HTTTA)·(phen)]n(2)(H3 TTTA = 2,2',2''-[1,3,5-triazine-2,4,6-triyltris(thio)] tris-acetic acid, phen = 1,10-phenanthroline) have been synthesized and characterized by elemental analysis, IR, powder XRD and single-crystal X-ray diffraction. Complex 1 consists of one CdII ion, one HTTTA2-ligand and one phen co-ligand. The Cd(Ⅱ) metal clusters were bridged by the tridentate HTTTA2-ligands into infinite 1D chains, which are further connected into the 3D architecture by abundant hydrogen bonds. In 2, three carboxyl groups of HTTTA2-ligand show different coordination directions because of the C–S–C flexible bond angle, which leads to different 1D chains of 2. The strong π-π stacking interaction and four C–H···O hydrogen bonds connect the 1D chains into a 3D framework. The solid-state photoluminescence and catalytic properties were studied as well.