Multiple Color Emission of Mechanoluminescence and Photoluminescence from SrZnSO: Bi3+ for Multi-mode Anti-counterfeiting

Mechanoluminescence materials that emit light under mechanical stimulation have attracted widespread attention in sensing, anti-counterfeiting and imaging applications. In this study, a series of novel Sr1-xBixZnSO (0.001≤x≤0.1) samples were synthesized by the method of high temperature solid-state reaction. It is worth noting that the distortion degree of SrO3S3 octahedron was increased with increasing Bi3+ concentration, and the color manipulated Sr1-xBixZnSO which can emit different photoluminescence (blue to dark blue and finally red) and mechanoluminescence (orange to red) colors are obtained. Moreover, the deep traps can stably store and provide electronic supplement to shallow traps released under mechanical stimulated. Therefore, devices made of SrZnSO: Bi3+ phosphor and polydimethylsiloxane (PDMS) can be used as thermo-mechano-opto three-mode anti-counterfeiting. The ML intensity is linear to the external load, can be utilized for stress sensing or imaging.

Localized Deep and Shallow Traps of α-Peaks from Thermally Stimulated Current (TSC) Measurement on Thermoplastic Polymers

In this paper, trap levels around the glass transition temperature (Tg) of polymers have been characterized using Thermally Stimulated Current (TSC) technique. Deconvolution on α-peaks of the Tg for PE (-104 °C), plasticized PVC (-35 °C), PMMA (90 °C) and PET (96 °C) were carried out based on the first-order kinetic theory for non-Debye relaxation. Using temperature, T from TSC experimental data, we have successfully separated the α-peaks of the thermoplastic polymers. It is found that the complex curve of α-peaks can composed of four (4) to eight (8) sub peaks. Dominant sub peaks were identified at Tmax = -105 °C, -34 °C, 89 °C and 92 °C for PE, pPVC, PMMA and PET, respectively. These peaks show activation energy, Ea of shallow and deep trap centers ranged from 0.3 eV to 4.6 Ev where they represent the depolarization of localized dipoles and space charges relaxations in the polymers.

Nonlinear Photocarrier Dynamics and the Role of Shallow Traps in Mixed-Halide Mixed-Cation Hybrid Perovskites

<p>We examine the role of surface passivation on carrier trapping and nonlinear recombination dynamics in hybrid metal-halide perovskites by means of excitation correlation photoluminescence (ECPL) spectroscopy. We find that carrier trapping occurs on subnanosecond timescales in both control (unpassivated) and passivated samples, which is consistent within a shallow-trap model. However, the impact of passivation has a direct effect on both shallow and deep traps. Our results reveal that the effect of passivation of deep traps is responsible for the increase of the carrier lifetimes, while the passivation of shallow traps reduces the excitation density required for shallow-trap saturation. Our work demonstrates how ECPL provides details about the passivation of shallow traps beyond those available via conventional time-resolved photoluminescence techniques.</p>

Nonlinear Photocarrier Dynamics and the Role of Shallow Traps in Mixed-Halide Mixed-Cation Hybrid Perovskites

<p>We examine the role of surface passivation on carrier trapping and nonlinear recombination dynamics in hybrid metal-halide perovskites by means of excitation correlation photoluminescence (ECPL) spectroscopy. We find that carrier trapping occurs on subnanosecond timescales in both control (unpassivated) and passivated samples, which is consistent within a shallow-trap model. However, the impact of passivation has a direct effect on both shallow and deep traps. Our results reveal that the effect of passivation of deep traps is responsible for the increase of the carrier lifetimes, while the passivation of shallow traps reduces the excitation density required for shallow-trap saturation. Our work demonstrates how ECPL provides details about the passivation of shallow traps beyond those available via conventional time-resolved photoluminescence techniques.</p>

Nonlinear photocarrier dynamics and the role of shallow traps in mixed-halide mixed-cation hybrid perovskites

We examine the role of surface passivation on carrier trapping and nonlinear recombination dynamics in hybrid metal-halide perovskites by means of excitation correlation photoluminescence (ECPL) spectroscopy. We find that carrier...

Investigation of 1/f and Lorentzian Noise in TMAH-treated Normally-Off GaN MISFETs

A tetramethyl ammonium hydroxide (TMAH)-treated normally-off Gallum nitride (GaN) metal-insulator-semiconductor field-effect transistor (MISFET) was fabricated and characterized using low-frequency noise (LFN) measurements in order to find the conduction mechanism and analyze the trapping behavior into the gate insulator as well as the GaN buffer layer. At the on-state, the noise spectra in the fabricated GaN device were 1/fγ properties with γ ≈ 1, which is explained by correlated mobility fluctuations (CMF). On the other hand, the device exhibited Lorentzian or generation-recombination (g-r) noises at the off-state due to deep-level trapping/de-trapping into the GaN buffer layer. The trap time constants (τi) calculated from the g-r noises became longer when the drain voltage increased up to 5 V, which was attributed to deep-level traps rather than shallow traps. The severe drain lag was also investigated from pulsed I-V measurement, which is supported by the noise behavior observed at the off-state.

Short-Term Non-Decaying Mechanoluminescence in Li2MgGeO4:Mn2+

Trap-controlled mechanoluminescent (ML) materials characterized by reproducible mechanoluminescence (ML) after irradiation recharging have shown attractive prospects in applications including stress distribution visualization, stress-driven light sources, and anti-counterfeiting. However, these materials generally suffer from the difficulty of achieving non-decaying ML when subjected to continuous mechanical stimulation. Herein, we develop a trap-controlled reproducible ML material, Li2MgGeO4:Mn2+, and report its short-term non-decaying ML behavior. Investigation of trap properties suggests that the unique non-decaying ML behavior should arise from the deep traps existing in Li2MgGeO4:Mn2+, which provide electron replenishment for shallow traps that release small numbers of electrons during short-term cyclic friction. Our results are expected to provide a reference for the ultimate achievement of long-term non-decaying ML in such materials.