Full Visible Range Research Articles

A fully nanofiber-based ultrathin electronic patch for self-powered and multifunctional on-skin applications

On-skin electronics that simultaneously ensure biocompatibility and stable electrical operation on soft tissue is still challenging. This study introduces a dual-layered and natural material based nanofiber platform designed for multifunctional on-skin operation (from energy harvesting to transdermal drug delivery). The ultrathin electronic patch consists of polyaniline (PANI)-coated cellulose nanofibers and silk fibroin nanofibers. The top PANI/cellulose nanofiber layer, exhibiting the resistivity of 0.315 Ω·m and over 90 % light absorbance in full visible range, functions as a flexible electrode. The silk nanofiber layer offers the skin-compatibility and strong adhesion to biological tissues, along with the capability of drug-loading. The nanofiber mesh structure withstands mechanical deformation, including compression, stretching, and bending, while its porous nature enhances breathability and hygiene. The fully nanofiber-based electronic patch platform is flexible, adheres well to the skin, and conforms to curved surfaces. By integrating the conductive properties of PANI with the biocompatibility of silk fibroin, this dual-layered membrane enhances the efficacy of transdermal drug delivery while offering multifunctional capabilities such as energy harvesting in a triboelectric nanogenerator (TENG), programmable drug delivery, and thermal therapy. This innovative approach paves the way for advanced biomedical applications by combining multiple functionalities in a single platform.

Sufficient energy band utilization profited from spatially discrete heterogeneous interfaces to induce efficient photoelectrochemical water splitting for ZnIn2S4 photoanode

The applied possibility of ZnIn2S4 is improved in the photoelectrochemical (PEC) energy transfer filed through elevated light absorption, accelerating charges transfer and suppressed carrier recombination. Consequently, Sb2S3/ZnIn2S4/Cu2S ternary composite photoanode is obtained through the induction of Sb2S3/ZnIn2S4 and ZnIn2S4/Cu2S heterogeneous interfaces at different spatial locations in ZnIn2S4, which enhances photocurrent density of ZnIn2S4-based photoanode to 2.81 mA/cm2 from 0.15 mA/cm2 with the nearly full visible spectrum absorption range of ∼ 776 nm. The deposition of Sb2S3 leads to enhanced quantum efficiencies, carrier diffusion time, and number of surface states. The loading of Cu2S top layer predominantly results in optimized surface states style and holes injection efficiency of SS/ZIS/CS. The comprehensive measurements and density functional theory (DFT) calculation demonstrate Sb2S3 and Cu2S are together employed to enhance the hybridization efficiencies of energy bands, accelerate charge transfer, revise the reaction sites, reduce free energy barrier of rate-determining steps and reaction over potential of ZnIn2S4 to enhance PEC water spitting. This work pioneers the construction of ZnIn2S4-based multijunction photoanodes with sufficient energy band utilization and confirms the conspicuous prospect for remaining photoanodes.

Colored thermal camouflage and anti-counterfeiting with programmable In3SbTe2 platform

Abstract Camouflage is an important technology in various scenarios. Usually, this involves the visible compatibility of the background, which however is facile under infrared thermal radiation detection. The simultaneous visible and thermal camouflage are challenging because it requires full and decoupled manipulations of visible reflection and infrared emissivity using one single device, let alone to its adaptivity to complex environments. Here, we report a programmable, colored thermal camouflage at 3–5 μm and 8–14 μm based on mode coupling in phase-change In3SbTe2 materials. A series of industry-friendly colored multilayer thermal emitters are designed consisting of an anti-reflectance layer for structure coloration above a coupled nanocavity for IR modulation, which easily realizes the complete decoupled control of visible color and infrared emissivity. Our solution features independent structural visible colors in the full visible range and continuously programmable dual-band emissivity modulation with up to 90 % absolute tuning range. Our work facilitates near optimal camouflage and anti-counterfeiting solution for visible-infrared multi-band compatibility of complex environments under different temperatures and colored appearances.

Full visible range two-dimensional electronic spectroscopy with high time resolution.

Two-dimensional electronic spectroscopy (2DES) is a powerful method to study coherent and incoherent interactions and dynamics in complex quantum systems by correlating excitation and detection energies in a nonlinear spectroscopy experiment. Such dynamics can be probed with a time resolution limited only by the duration of the employed laser pulses and in a spectral range defined by the pulse spectrum. In the blue spectral range (<500 nm), the generation of sufficiently broadband ultrashort pulses with pulse durations of 10 fs or less has been challenging so far. Here, we present a 2DES setup based on a hollow-core fiber supercontinuum covering the full visible range (400-700 nm). Pulse compression via custom-made chirped mirrors yields a time resolution of <10 fs. The broad spectral coverage, in particular the extension of the pulse spectra into the blue spectral range, unlocks new possibilities for coherent investigations of blue-light absorbing and multichromophoric compounds, as demonstrated by a 2DES measurement of chlorophyll a.

Diffraction-based nonlinear model for the design of broadband adiabatic up-conversion imaging.

In recent years, mid-infrared parametric upconversion imaging, a nonlinear optical method that involves converting mid-infrared light into visible images, has significantly advanced and has shown considerable potential for various applications, including biomedical imaging and remote sensing. While diffraction-based parametric upconversion imaging modeling in standard thin birefringence crystals have been addressed, the numerical framework developed so far fails to address long aperiodic poled crystals. Specifically, diffraction-based analysis of the recent broadband adiabatic frequency upconversion imaging, which allows simultaneous image upconversion of extremely broadband signals is still lacking. Here, we introduce a diffraction-based numerical simulation framework for predicting the evolution of the nonlinear image/signal generation in upconversion imaging systems. This generalized framework can handle both periodically and aperiodically poled crystal designs. Specifically, the model captures faithfully and addresses the varying image magnification arising from upconversion at a Fourier plane of a multiwavelength object. The numerical simulations are validated by experimental measurements of broadband upconversion 3-5 µm mid-IR images to the visible-NIR, showing a good agreement. Moreover, the model allows the exploration of the trade-offs in the spectral span when moving to the full visible range. Our numerical framework will be useful for the interpretation of experimental results obtained in an imaging setting with nonlinear optical elements.

Coherent heteroepitaxial growth of I-III-VI2 Ag(In,Ga)S2 colloidal nanocrystals with near-unity quantum yield for use in luminescent solar concentrators

Colloidal Ag(In,Ga)S2 nanocrystals (AIGS NCs) with the band gap tunability by their size and composition within visible range have garnered surging interest. High absorption cross-section and narrow emission linewidth of AIGS NCs make them ideally suited to address the challenges of Cd-free NCs in wide-ranging photonic applications. However, AIGS NCs have shown relatively underwhelming photoluminescence quantum yield (PL QY) to date, primarily because coherent heteroepitaxy has not been realized. Here, we report the heteroepitaxy for AIGS-AgGaS2 (AIGS-AGS) core-shell NCs bearing near-unity PL QYs in almost full visible range (460 to 620 nm) and enhanced photochemical stability. Key to the successful growth of AIGS-AGS NCs is the use of the Ag-S-Ga(OA)2 complex, which complements the reactivities among cations for both homogeneous AIGS cores in various compositions and uniform AGS shell growth. The heteroepitaxy between AIGS and AGS results in the Type I heterojunction that effectively confines charge carriers within the emissive core without optically active interfacial defects. AIGS-AGS NCs show higher extinction coefficient and narrower spectral linewidth compared to state-of-the-art heavy metal-free NCs, prompting their immediate use in practicable applications including displays and luminescent solar concentrators (LSCs).

Sn2+/Mn2+ co-doped germanate glass with quasi-sunlight spectrum visible-emission and its high-quality w-LED application

Light sources with the spectrum distribution approaching the sunlight, even in the visible range, are preferred. Up to now, sunlight simulator is still a great challenge to the scientists. In this work, the Sn2+/Mn2+ doped germanate glasses with the emission near to the sunlight spectral distribution in the visible wavelength region were developed, and the corresponding applications in w-LEDs were demonstrated. The spectral properties including excitation and emission characteristics, concentration quenching, fluorescence dynamics for Sn2+ and Mn2+ single-doped germanate glasses were studied. It is found that both Sn2+ and Mn2+ single-doped glasses can be effectively excited by broadband ultraviolet and subsequently generate broadband visible emissions. However, the emission from each of single-doped glasses does not cover full visible wavelength range. Fortunately, it is found that the lack of the red spectral component in the broadband visible emission of Sn2+ single-doped glass can be compensated by the broadband red emission of Mn2+. On that base, the Sn2+/Mn2+ co-doped germanate glasses were fabricated and studied. Broadband emission covering full visible range, good luminescence thermal stability and excellent chromatic performance were realized in the co-doped glasses by optimizing concentration and engineering energy transfer. Finally, a prototype w-LED was assembled by the Sn2+/Mn2+ co-doped germanate glass and a 310 nm LED chip. The prototype w-LED reveals the sunlight-like visible spectrum, good color coordinates (0.380, 0.371), low correlated color temperature (CCT) of 3811 K and high color rendering index of 95.3, indicating that the Sn2+/Mn2+ co-doped germanate glasses are promising candidate to develop high performance w-LED.

Remarkable luminescence regulation covering full visible wavelength range of zero-dimensional indium-based metal halides

Recently, there has been a lot of research into the use of zero-dimensional (0D) metal halides as new luminous materials. However, the wide-range tunability of luminescence properties by structural engineering need to be explored. Here, we report the vacuum solid-state reaction synthesis of a series of indium-based A3InX6 (A = K, Rb, or Cs; X = Cl, Br, or their mixture) 0D metal halide single crystals (SCs). Alkali metal substitution at A site leads to similar luminescence properties but very different stability, among which Rb3InCl6 was the most air stable. Halogen alloying at the X site of Rb3InX6 can produce a luminescence wavelength modulation from 436 to 505 nm. The luminescence wavelength was further extended by Sb3+ doping to the 509–622 nm region. Finally, due to the high luminescence tunability covering the full visible wavelength range, we achieved pure white light-emitting diodes utilizing a combination of Rb3InBr2Cl4 and Rb3InBr2Cl4:Sb3+ SCs. This work provides a strategy with simultaneous substitution, alloying, and doping to modulate the luminescence properties of 0D lead-free metal halides for a variety of applications.

Anisotropic emission of orientation-controlled mixed-dimensional perovskites for light-emitting devices

Perovskite light-emitting diodes (PeLEDs) are attracting increasing attention owing to their impressive efficiencies and high luminance across the full visible light range. Further improvement of the external quantum efficiency (EQE) of planar PeLEDs is limited by the light out-coupling efficiency. Introducing perovskite emitters with directional emission in PeLEDs is an effective way to improve light extraction. Here, we report that it is possible to achieve directional emission in mixed-dimensional perovskites by controlling the orientation of the emissive center in the film. Multiple characterization methods suggest that our mixed-dimensional perovskite film shows highly orientated transition dipole moments (TDMs) with the horizontal ratio of over 88%, substantially higher than that of the isotropic emitters. The horizontally dominated TDMs lead to PeLEDs with exceptional high light out-coupling efficiency of over 32%, enabling a high EQE of 18.2%.

Broadband Flexible CuPc–PCBM Photodetector With Responsivity in Different Spectral Regions

Organic photodetectors have gained immense attention in the field of organic electronics because of their diverse applications, like image sensing, optical communication, health monitoring, and so on. These types of devices possess tunable photophysical and optoelectronic properties. Considering the mechanical flexibility, lightweight, and high performance of polyethylene terephthalate (PET) as substrate, a flexible organic photodetector (OPD) with diode architecture involving Copper phthalocyanine (CuPc) as the donor and Phenyl-C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">60</sub> -butyric acid methyl ester (PC <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">60</sub> BM) as the acceptor has been fabricated. The maximum EQE of 10.2% was perceived. The OPD exhibited a decent spectral response in the full visible range with the highest value at ~385nm. Characteristics of this flexible OPD with an active organic layer and conducting polymer-based hole transport layer have been explored thoroughly under the different spectral ranges of the solar spectrum.

SOAP-GPU: Efficient spectral modeling of stellar activity using graphical processing units

Context. Stellar activity mitigation is one of the major challenges in the detection of Earth-like exoplanets in radial velocity measurements. Several promising techniques are being developed to investigate the use of spectral time series and differentiate between stellar and planetary perturbations. In this context, developing a software that can efficiently explore the parameter space of stellar activity at the spectral level is of great importance. Aims. The goal of this paper is to present a new version of the Spot Oscillation And Planet (SOAP) 2.0 code that is able to model stellar activity at the spectral level using graphical processing units (GPUs). Methods. We took advantage of the computational power of GPUs to optimise the computationally expensive algorithms behind the original SOAP 2.0 code. For that purpose, we developed GPU kernels that allow for stellar activity to be modeled on any given wavelength range. In addition to the treatment of stellar activity at the spectral level, SOAP-GPU also includes a change of spectral line bisectors from center to limb. It can also take PHOENIX spectra as input to model the quiet photosphere, spots, and faculae, allowing for simulations of stellar activity for a wider space in terms of stellar properties. Results. Benchmark calculations show that for the same accuracy, this new code improves the computational speed by a factor of 60, as compared to a modified version of SOAP 2.0 that generates spectra, when modeling stellar activity on the full visible spectral range with a resolution of R = 115 000. Although the code now includes the variation of spectral line bisector with center-to-limb angle, the effect on the derived RVs is minimal. We also show that it is not possible to fully separate the flux from the convective blueshift effect when modeling spots, due to their lower temperature and the subsequent appearance of molecular absorption in their spectra. Shown to be rather negligible for the Sun, this degeneracy between the flux and convective blueshift effect becomes more important when we move to cooler stars. However, this issue does not impact the estimation of the total effect (flux plus convection), demonstrating that users can trust this output. Conclusions. The publicly available SOAP-GPU code allows us to efficiently model stellar activity at the spectral level, which is essential for testing further stellar activity mitigation techniques at the level of spectral time series that are not affected by other sources of noise. Besides a huge gain in performance, SOAP-GPU also includes more physics and is able to model different stars than the Sun, from F to K dwarfs, thanks to the use of the PHOENIX spectral library. However, we do note that due to the limited understanding of stellar convection and activity on other stars than the Sun, the more we move away from the solar case and the more carefully we ought to consider the output of the code.

Novel noble-metal-free Co2P/CdIn2S4 heterojunction photocatalysts for elevated photocatalytic H2 production: Light absorption, charge separation and active site

Constructing heterojunctions is an effective and controllable approach that can boost the activity of photocatalysts. Inspiringly, this study explored a simple method that can be used to construct novel noble-metal-free Co2P/CdIn2S4 (CPCIS) heterojunction photocatalysts for photocatalytic hydrogen production. The heterojunction was formed by loading CdIn2S4 (CIS) nanoparticles on the surface of Co2P (CP). The structure, morphology, and optical property of the as-prepared samples were characterized by a series of tests. The DRS results showed that, the light absorption range of CPCIS was extended to the full visible light range and its light absorption intensity obviously was enhanced at 500–800 nm. The PL and photoelectrochemical tests manifested that the formed heterojunction promoted the separation of charges. The LSV results indicated that CP reduced the H2 evolution overpotential of the composites. Besides, CP could serve as active sites of H2 evolution in heterojunction composites. Interestingly, the H2-evolution rate for the optimum CPCIS (471.87 μmol h−1 g−1) was around 3.6 times than CIS-Pt. The elevated activity of CPCIS may mainly attribute to the following aspects: its enhanced light absorption, elevated charge separation and increased active site. More importantly, the photocatalytic activity of heterojunction composites didn’t almost decrease after three cycles. This article delivers an idea that can be applied to form heterojunctions between CP and other sulfides for photocatalytic H2 production, easily extending to other transition metal phosphides.

Nano‐Confined Growth of Perovskite Quantum Dots in Transparent Nanoporous Glass for Luminescent Chemical Sensing

AbstractPrior nano‐confined matrices for perovskite quantum dots (QDs) dealt only with powders or thin films, which usually suffer from poor handling properties and high transparency limitations for integrating into optical devices. Here, the nano‐confined growth of perovskite QDs in an optically transparent, robust, and monolithic matrix by using nanoporous glass (NG) as a nano‐reactor is demonstrated. Owing to quantum confinement effects in the inherent nanoporous network, rapid nanoconfined low‐temperature solution‐processed perovskite QDs could synthesize spontaneously. The binding energy of CsPbBr3 QDs in NG has been enhanced to ≈177.2 meV due to the confinement effect. The nano‐channels enable the tunable mono/multi‐color emission in full visible range via pore size tailoring or post‐halide exchange. Considering the fast diffusion of nanoporous channels and enhanced stability in this processable monolithic composite, a rapid‐response and reusable red‐green switching light‐emitting diode (LED) sensor for halomethanes is demonstrated. The rational design of perovskite NG via this efficient nano‐confined route results in a new optoelectronic device‐relevant material platform.

Self-Healing Chameleon Skin Functioning in the Air Environments

Chameleons are famous for their uncommon ability to change skin colors rapidly by tuning the lattice distance of guanine nanocrystals within the dermal iridophores. This mechanism has inspired various artificial photonic crystal (PC) films with tunable structural colors. However, the structural colors of most reported films are facile to be destroyed by external factors such as friction, impact, or water evaporation. Herein, an artificial intelligent skin, which has an elastomer–colloidal photonic crystal–hydrogel sandwich structure, is presented in this work. The outer modified polydimethylsiloxane layer acts as the cuticle to protect the hydrogel layer from water evaporation and endows the skin with self-healing ability. The inner hydrophilic hydrogel layer embedded with the colloidal photonic crystals acts as the dermis layer, and the polystyrene colloids layer plays the role of the guanine nanocrystals. A programmed color change can be easily controlled by varying the elongation of the artificial skin, covering the full visible spectrum range. Moreover, skin with patterned stripes, which is similar to the panther chameleon skin that can manipulate multiple colors, has also been achieved. The present artificial skin will offer fresh perspectives on the preparation of artificial chameleon skin similar to the real dynamic flexible skin, which would promote the application of PCs in optical devices.

PO15: Systematic Dwell Position Deviation of Elekta MR Compatible HDR Ring Applicators

<h3>Purpose</h3> (1) To identify a systematic dwell position deviation of Elekta MR compatible HDR ring applicators due to its design and (2) to demonstrate the dosimetric impact of the deviation. <h3>Materials and Methods</h3> In these ring applicators, the source is designed to travel precisely along the central axis of the ring tube. However, the actual source positions deviate from the central axis due to the semi-rigid design of the wire carrying the source. To quantify the deviation, in-house QA devices were built using decommissioned ring applicators of three different diameters (26mm, 30mm, and 34mm). The ring applicators were modified by replacing their top caps with a 1 mm thick transparent plastic plate. This allowed proper visualization of both the vendor-provided wire QA markers and the actual Ir-192 source. The high-resolution camera of the Elekta Flexitron system was used to acquire images of the applicator and the source. The source was driven to dwell positions with a 5 mm increment to cover the full visible range of the ring. An image was acquired at each dwell position. This procedure was repeated 5 times for each ring size. Two observers independently measured the arc length traveled by the source from the first dwell position to other dwell positions. The deviation was calculated as the difference between the measured arc length and the intended dwell position (converted to arc length). <h3>Results</h3> The deviation was found to be a function of the arc distance from the first dwell position. It increases almost linearly with arc length, experiences a sharp increase before settling in a range between 5 mm and 6 mm. Up to 6 mm deviation was found for ring applicators of all three different diameters. Although there were small interobserver differences (mean = 0.1 mm, SD = 0.13 mm), the results were highly reproducible (SD = 0.09 mm). The dwell position deviations result in remarkable differences of the isodose curves surrounding the ring applicator. The measured deviations were applied to our library plan for cervical cancer using 30 mm ring and 60 mm tandem. The isodose lines in the plane of the ring before and after the offsets were applied are shown in figure 1(a) and (b), respectively. <h3>Conclusions</h3> Large systematic dwell positions deviations of the Elekta MR compatible HDR ring applicators has been quantified. These deviations may have significant dosimetric impact on HDR treatment. Therefore, they should be considered by the treatment planning system for more accurate dose computations.

Super-multiplexing excitation spectral microscopy with multiple fluorescence bands.

Fluorescence microscopy, with high molecular specificity and selectivity, is a valuable tool for studying complex biological systems and processes. However, the ability to distinguish a large number of distinct subcellular structures in a single sample is impeded by the broad spectra of molecular fluorescence. We have recently shown that excitation spectral microscopy provides a powerful means to unmix up to six fluorophores in a single fluorescence band. Here, by working with multiple fluorescence bands, we extend this approach to the simultaneous imaging of up to ten targets, with the potential for further expansions. By covering the excitation/emission bandwidth across the full visible range, an ultra-broad 24-wavelength excitation scheme is established through frame-synchronized scanning of the excitation wavelength from a white lamp via an acousto-optic tunable filter (AOTF), so that full-frame excitation-spectral images are obtained every 24 camera frames, offering superior spectral information and multiplexing capability. With numerical simulations, we validate the concurrent imaging of 10 fluorophores spanning the visible range to achieve exceptionally low (∼0.5%) crosstalks. For cell imaging experiments, we demonstrate unambiguous identification of up to eight different intracellular structures labeled by common fluorophores of substantial spectral overlap with minimal color crosstalks. We thus showcase an easy-to-implement, cost-effective microscopy system for visualizing complex cellular components with more colors and lower crosstalks.

High-color-rendering white light and broadband optical gain of Ag-aggregates/Mn2+ co-doped germanate glasses

Ag-aggregates and Mn2+ doped germanate glasses were prepared by a melt-quenching method, and their spectroscopic and chromatic properties were studied. It was found that Ag-aggregates doped samples exhibited broadband emission covering almost the visible spectral range. When Mn2+ with 4T1(4G) to 6A1(6S) transition was introduced, the broadband emission of Ag-aggregates doped germanate glass was further extended in red light range. Meanwhile, the luminescence color coordinate and correlated color temperature (CCT) of Ag-aggregates/Mn2+ co-doped sample excited by 360 nm were derived to be (0.33, 0.32) and 5616.7 K, respectively, and its color rendering index (CRI) is up to 93. Moreover, the optical gain at various wavelengths was investigated based on an amplified spontaneous emission (ASE) technique, and the Ag-aggregates/Mn2+ co-doped sample possesses broadband optical gain in full visible range. These results indicate that Ag-aggregates/Mn2+ co-doped germanate glasses are promising candidates for applications in white light-emitting-diodes (wLEDs) and broadband tunable lasers.

Tunable and high-color-rendering white light emissions in full visible spectral range in Ag-aggregates/Sm3+ co-doped germanate glass fluorophors

To achieve a tunable and high-color-rendering white light emission in full visible spectral range, the Ag-aggregates/Sm3+ co-doped germanate glass fluorophors were prepared by a melt-quenching method. Under the excitation of different wavelengths, the intense broadband emissions covering full visible spectral range from blue to red were gained in the germanate glasses only containing Ag-aggregates. From the optical spectral analyses, it was found that with increasing the excitation wavelengths, the emission peak position exhibits red-shift. However, the red component in the emission spectra is still of relative lack for realizing high quality white light, therefore Sm3+ was introduced as co-dopant to supply the red spectral component. In this way, a series of chroma-tunable and full-color-emitting white lights with color coordinates from (0.26, 0.25) to (0.30, 0.32) were successfully realized based on adjusting the excitation wavelengths and Sm3+ concentration. Particularly, the color rendering index (CRI) up to 97.6 was achieved. Furthermore, the luminescence thermal stability of Ag-aggregates/Sm3+ co-doped germanate glass fluorophors was investigated based on the Arrhenius model, and the corresponding ΔE values for Ag aggregates and Sm3+ emissions were confirmed to be 0.25 and 0.19 eV, respectively. In addition, a temperature sensing model was established based on the luminescence intensity ratio of Ag-aggregates to Sm3+, and the thermochromatic property of Ag-aggregates/Sm3+ co-doped germanate glasses was also evaluated. It was found that the luminescence color coordinates of Ag-aggregates/Sm3+ co-doped glass fluorophors always lie in the white light region when the sample temperature increases from 301 to 693 K, thus indicating that Ag-aggregates/Sm3+ co-doped glass fluorophors have potential application in solid-state lighting sources as a single-component white lighting material.

Synthesis and intriguing single-component white-light emission from oxadiazole or thiadiazole integrated with coumarin luminescent core

There has been evidence of non-typical fluorescence activities in thiadiazole and oxadiazole derivatives. Also, some coumarin compounds with tunable luminescence properties via controlling the molecular structure and its aggregation have been recently reported. As a result, our effort concentrated on integrating these moieties in order to improve the applicability of the target compounds through easy synthetic schemes. All the synthesized derivatives underwent extensive spectrum analysis, including NMR, FT-IR, and mass spectroscopy. DFT calculations, UV–visible, and luminescence spectroscopy were used to study the photophysical characteristics of three compounds having coumarin luminescent core integrated with the thiadiazole, oxadiazole, or hydrazinecarbothioamide. We found that manipulating the packing of a compound under specific conditions (e.g., the solid state or moderate solution concentration of compounds containing the heterocyclic substituent “thiadiazole or oxadiazole”) can trigger processes related to the way the molecules interact, resulting in the appearance of dual or multiple fluorescence bands that cover the full visible range. Additionally, we deduced that the intriguing white emission from a single component might be generated by modifying the degree of molecular aggregation to balance the relative band intensities at short and long wavelengths. Long-wavelength emission arises from aggregated molecules whereas short-wavelength emission results from single molecules. It is evident that this balance is feasible in both the solid form of the thiadiazole derivative and 1 × 10–5 mol L–1 solution of the oxadiazole derivative. Hence, this research proposes an easy method for creating the intriguing white-light emission from a single component.

Stable CsPbX3 mixed halide alloyed epitaxial films prepared by pulsed laser deposition

The pulsed laser deposition (PLD) technique has been proved to be able to grow oxide thin films with high structural quality with precisely controlled composition and thickness to achieve designed optical and electronical properties established in alloyed semiconductors and heterostructures. In this Letter, inorganic halide perovskite CsPb(IxClyBr1−x−y)3 epitaxial alloyed films on (001)-SrTiO3(STO) substrates were grown by PLD. The film crystal quality, phase stability, and the epitaxial relationship between the film and substrate were characterized with a detailed x-ray diffraction technique like high-resolution reciprocal spatial mapping and ϕ-scan. In addition, the photocarrier dynamics of the alloyed epitaxial films were investigated by photophysics spectroscopy, including steady and femtosecond transient optical absorption spectroscopy and temperature-dependent and time-resolved photoluminescence spectroscopy. The bandgap of the CsPbX3 films was tuned from 1.75 to 2.98 eV by substituting X with I/Br/Cl and their mixture of different ratios. Free exciton emissions were observed at a low temperature photoluminescence spectrum (PL, 10 K), which confirmed the high crystal and optical quality of the epitaxial perovskite alloyed films except the CsPbI3 film. The femtosecond transient absorption spectra also showed that such perovskite films are of very low concentration of exciton trap states. These results indicated that PLD is a powerful technology for growing high quality inorganic halide perovskite films with a tunable bandgap covering the full visible light range, which provided more options for CsPbX3 based panchromatic LED and other optoelectronic devices.