Applications In Optoelectronic Devices Research Articles

Exploring the effect of thin film thicknesses on linear and nonlinear optical properties of MoO3 thin film

The structural, morphological, linear, and nonlinear optical properties of MoO3 thin films deposited by thermal deposition were measured. The effect of various thicknesses of films was studied. The structural and morphological parameters of films, determined by x-ray diffraction, field emission scanning electron microscopy, and AFM images, are compared to the linear and nonlinear optical characteristics of these media. The bandgap of the prepared thin films was obtained from the diffuse reflectance spectroscopy spectra. The electron’s effective mass (me*/m0), linear refractive index (n0), and optical static and high frequency dielectric constant (ɛ0, ɛ∞) values were calculated by using the bandgap energy values. Increasing the thicknesses of thin films decreased the bandgap, increased the root mean square, and increased the size of nanoparticles and the nonlinear response of thin films. The high magnitude of n2 and β was because of MoO3 (300 nm-thickness), which were of the order of 10−5 cm2/W and 10−1 cm/W, respectively. The fluctuations in nonlinear responses observed at different thicknesses are attributed to d–d transitions and intraband scattering of equilibrium electrons influenced by laser radiation, as indicated by the nonlinearity data. The considerably elevated refractive nonlinearity values in the analyzed film materials suggest their potential for practical application in optoelectronic devices.

Donor-acceptor-donor type AIEgens based on thieno[3.4-c]pyrrole-4,6-dione: Synthesis, electropolymerization, and electrochromism.

Photoelectric functional materials with electrochemical reversible activity and fluorescence intensities have attracted significant interest due to their wide range of applications in optoelectronic devices. In this work, a series of photoresponsive and electroactive monomers based on thieno[3.4-c]pyrrole-4,6-dione (TPD) are synthesized and characterized. They possess planar geometry with smaller dihedral angles owing to the existence of a noncovalent conformation lock coming from the S atoms and the O atoms. Crystallographic, spectroscopic, and computational results reveal that the introduction of the TPD unit can endow the monomers with aggregation-induced emission (AIE), reduced energy levels, and increased electrochemical activity. The monomers were successfully polymerized through the electrochemical method, and the corresponding polymers displayed reversible electrochemical activity and stability. Moreover, polymer films based on 3,3-dimethyl-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxepine (ProE)-TPD have electrochromic properties in the near-infrared field with a high value of optical contrast ratio (∆T) of 27.1% at 1000 nm.

Investigating the potential of Nd and Co modified bismuth ferrite (BiFeO3) nanoparticles for advanced energy storage and electronic applications

In this study, we synthesized and characterized Nd and Co modified bismuth ferrite nanoparticles (BNFCO) using mechanical milling. X-ray diffraction (XRD) analysis has provided confirmation of the distorted rhombohedral, mixed rhombohedral-tetragonal and tetragonal perovskite structure with space group R3c and P2mm. Notably, these nanoparticles exhibited a high dielectric constant and low loss values at low frequencies and high temperatures, remaining around 103 up to 373 K before increasing to approximately 104, which opens new avenues for exploring temperature-sensitive dielectric properties. The AC conductivity adhered to Jonscher's power law, with dc conductivity values ranging from 10−5 to 10−3 s/cm, representing a significant advance in understanding electrical conduction in nanomaterials. Furthermore, we assessed the electrochemical behavior of the fabricated samples at varying concentrations using cyclic voltammetry, Galvanostatic charge and discharging (GCD), and electrochemical impedance spectroscopy (EIS) on a modified electrode. BNFCO (0.20) displayed exceptional properties with a capacitance of 510 F g−1 and a capacitance retention of 93.9 % after 5k cycles, making BNFCO nanomaterials potential candidates for supercapacitor applications. The multifunctional properties of Nd and Co modified bismuth ferrite nanoparticles presented in this study offer unparalleled opportunities for transformative applications in supercapacitors and optoelectronic devices.

Structural and photoelectric properties of hybrid halide perovskites CsxMA1-xMgyPb1-yI3 from first-principles

Lead toxicity and stability are important issues to be addressed in organic/inorganic hybrid perovskite solar cell materials. In this study, the electronic, structural, and optical properties of Cs and Mg co-doped organic/inorganic hybrid perovskites were investigated through first-principles calculations. The synergistic effect of (Cs, Mg) doping improves the lattice stability, reduces the content of elemental lead, thereby reducing environmental pollution, and induces a tunable band gap of 0.96–2.58 eV. Perovskite with a bandgap of 1.5–1.6 eV is an ideal adsorbent for solar cells, while that with a bandgap greater than 1.70 eV can be used for perovskite-silicon tandem solar cells. Co-doping of Cs and Mg compresses the neighboring Pb–I and Mg–I bond and distorts the [PbI6] octahedra. The organic/inorganic hybrid perovskites co-doped with cesium and magnesium significantly increase the light absorption coefficients in the near-ultraviolet and visible regions. The predicted Cs and Mg co-doped halide perovskites with intriguing properties would become a promising candidate for applications in solar cells and optoelectronic devices.

Ultrasensitive Self-Powered Flexible Crystalline β-Ga2O3-Based Photodetector Obtained through Lattice Symmetry and Band Alignment Engineering.

Due to its portable and self-powered characteristics, the construction of Ga2O3-based semiconductor flexible devices that can improve the adaptability in various complex environments have drawn great attention in recent decades. However, conventional Ga2O3-based flexible heterojunctions are based on either amorphous or poor crystalline Ga2O3 materials, which severely limit the performance of the corresponding devices. Here, through lattice-symmetry and energy-band alignment engineering, we construct a high-quality crystalline flexible NiO/β-Ga2O3 p-n self-powered photodetector. Owing to its suitable energy-band alignment structure, the device shows a high photo-to-dark current ratio (1.71 × 105) and a large detection sensitivity (6.36 × 1014 Jones) under zero bias, which is superior than most Ga2O3 self-powered photodetectors even for those based on rigid substrates. Moreover, the fabricated photodetectors further show excellent mechanical stability and robustness in bending conditions, demonstrating their potential practical applications in flexible optoelectronic devices. These findings provide insights into the manipulation of crystal lattice and energy band engineering in flexible self-powered photodetectors and also offer guideline for designing other Ga2O3-based flexible electronic devices.

The dual role of Dy3+ in a novel Sr2Al2SiO7:Eu2+, Dy3+ long-persistent luminescence glass–ceramic

A novel Sr2Al2SiO7:Eu[Formula: see text], Dy[Formula: see text] long-persistent luminescence (LPL) glass–ceramic has been successfully synthesized by the recrystallization-melting method in the SrO-Al2O3-SiO2-B2O3-Li2O glass system. The glass–ceramic form enhances the plasticity of the material compared to traditional Sr2Al2SiO7:Eu[Formula: see text], Dy[Formula: see text] phosphorescence powders. Additionally, the Dy[Formula: see text] ions serve a dual role as fluorescence emission centers and sensitizers for afterglow. By controlling the concentration of Dy[Formula: see text], the characteristic fluorescence intensity can be adjusted to achieve color-tunable photoluminescence. Besides, Dy[Formula: see text] ions, as trap centers, capture the electrons, resulting in a longer afterglow than the Eu[Formula: see text] singly doped sample. After exposure to ultraviolet light, the initial brightness intensity of the Dy:Eu = 16:1 sample increases to 1525 mcd/m2, and the emission lasts for 30 min. These optimized bulk materials, with unique luminous properties, have potential applications in future optoelectronic devices.

Cu2O/TiO2 core–shell nanowire heterojunction for high-performance self-powered photodetector

High-performance self-powered photodetectors (PDs) have great commercial value in optical communication, intelligent sensing and medical diagnosis. However, the limited active area of traditional thin film heterojunction seriously restricts the photoelectric performance of the detector. In this paper, the Cu2O/TiO2 core-shell nanowire (NW) heterojunction PD was synthesized for the first time by simple hydrothermal and electrochemical deposition methods, which effectively improved the response performance and response speed of the device based on its broad photoactive area and ordered carrier transport path. The PD exhibits significant diode behavior, with rectification ratios of 543 at ±2 V. The responsivity is as high as 6.8 mA W−1 at zero bias under 490 nm illumination. The short rise and decay times measured are 0.09 and 0.18 s at zero bias, respectively. Obviously, this low-cost, high-performance self-powered Cu2O/TiO2 core-shell NW heterojunction PD shows great promise in future optoelectronic device applications.

Real-time detection of aging status of methylammonium lead iodide perovskite thin films by using terahertz time-domain spectroscopy

The inadequate stability of organic–inorganic hybrid perovskites remains a significant barrier to their widespread commercial application in optoelectronic devices. Aging phenomena profoundly affect the optoelectronic performance of perovskite-based devices. In addition to enhancing perovskite stability, the real-time detection of aging status, aimed at monitoring the aging progression, holds paramount importance for both fundamental research and the commercialization of organic–inorganic hybrid perovskites. In this study, the aging status of perovskite was real-time investigated by using terahertz time-domain spectroscopy. Our analysis consistently revealed a gradual decline in the intensity of the absorption peak at 0.968 THz with increasing perovskite aging. Furthermore, a systematic discussion was conducted on the variations in intensity and position of the terahertz absorption peaks as the perovskite aged. These findings facilitate the real-time assessment of perovskite aging, providing a promising method to expedite the commercialization of perovskite-based optoelectronic devices.Graphical

Thickness-modulated electronic band structures and exciton behavior of non-van-der-waals 2D Bi2O2Se films

Bi2O2Se, as a non-van-der-waals (non-vdW) interlayer coupling two-dimensional material, its electronic band structures and exciton behavior still merit further in-depth studies, especially in the consideration of thickness tuning degrees of freedom. Here, we reveal the broadband excitonic performance and critical point properties of Bi2O2Se films with different thicknesses (3.54–16.33 nm). Five critical points are determined and assigned to specific optical transitions. Moreover, we observe that electronic bandstructures in the Γ valley are stable with variable thicknesses, while the deeper electron levels received more pronounced thickness modulation. And we first report four excitons in wide spectral range (1.24–6.20 eV) through absorption coefficient fitting. Significantly, due to the strong localization of electrons and holes induced by the intralayer built-in electric field, the exciton binding energy (Eb) value of 3.54 nm-Bi2O2Se (234 meV at Γ position) is apparently larger than typical multi-layer TMDCs, which offering unprecedented opportunities in applications in optoelectronic devices. Furthermore, Eb of two excitons at low energy region (Eb1, Eb2) red-shift with increasing thickness, while Eb of higher-energy excitons (Eb3, Eb4) blue-shift, owing to the dispersion characteristic of the effect dielectric screening effects. Our results are vital to wide-ranging applications of Bi2O2Se from fundamental science to optoelectronic devices.

First‐Principles Study on the Effects of Different Valence Hi and VO on the Mobility, Conductivity, and Carrier Lifetime of β‐Ga2O3: Mo5+/6+

The poor conductivity of β‐Ga2O3 limits its application in optoelectronic devices. Currently, there have been advancements in investigating the impact of Mo doping on the photoelectric characteristics of β‐Ga2O3. However, there are few studies on the impact of different valence states of Mo doping and the coexistence of O vacancy and interstitial H on the electrical properties of β‐Ga2O3. In the process of preparing β‐Ga2O3, O vacancy and interstitial H inevitably exist. In response to these problems, the first‐principles GGA + U method is used to study the impact of different valence states of Mo doping and the coexistence of interstitial H and O vacancy on the electrical properties of β‐Ga2O3. The electronic structure, mobility, conductivity, and carrier lifetime of the system are calculated and analyzed. The results show that all doping systems are more stable under Ga‐rich conditions. The band gap of the Mo‐doped β‐Ga2O3 system gradually narrows, which is mainly attributed to the Burstein–Moss effect and the multiplicity reintegration effect. Mo doping effectively improves the electrical conductivity of the system. Ga47O72Mo16+H11+ system has the longest carrier lifetime; Ga47O72Mo16+H10 has the largest mobility; Ga47O72Mo15+H10 system has the highest conductivity. Therefore, Mo‐doped β‐Ga2O3 materials help to prepare new electrical performance devices.

Strain-bandgap quasi-linear correlation applied to modulation of NiBr2 monolayer optical properties

Recently, two-dimensional transition metal dihalides have shown diverse applications in spintronics, quantum devices, and optoelectronic devices. In this work, density functional theory (DFT) is adopted to investigate the effect of biaxial strain upon the electronic structure and optical properties of NiBr2 monolayer. The results show that NiBr2 is an indirect semiconductor with band gap 2.62 eV (DFT + U) and 3.18 eV (HSE06), which could vary quasi-linearly from 2.73 eV to 1.71 eV modulated by biaxial strain (6 % to −10 %). Combined with the analysis of the density of states (DOS), the primary reason for the alteration in the band gap is that strain significantly affects the behavior of Ni 3d electrons. When the strain changes from positive to negative, the DOS of Ni 3d shifts towards the Fermi level, resulting in a reduction in the band gap. Within this strain range, all of the optical properties exhibit a quasi-linear tendency similar to the band gap variation. The optical peaks of NiBr2 under compressive strain are not only red-shifted into the visible light (VL) region but also significantly enhanced in the VL and ultraviolet (UV) regions. Applying strain can greatly boost the electrical and optical properties of NiBr2 monolayer, making it a promising candidate in the field of ultraviolet detectors.

The electronic stopping power of self-irradiated molybdenum in different charge states

Molybdenum is not only an excellent photovoltaic material but also a crucial component in semiconductors. However, its high bandgap restricts its application in optoelectronic devices. This limitation arises primarily because the energy barrier between photogenerated electron-hole pairs cannot be directly overcome by sunlight. Self-irradiation can overcome these barriers, allowing efficient separation of photogenerated electrons and holes, making molybdenum an excellent light-absorbing material. By altering the charge state of molybdenum-based materials, their light absorption can be adjusted. This project aims to systematically study the optical properties and electronic stopping power of molybdenum-based materials in different charge states through theoretical calculations and experiments.

High performance ambipolar response photodetectors based on ReS2/PdSe2 van der Waals heterostructures

Anomalous negative photoresponse in a photodetector where the current is reduced under light illumination holds great potential in the application of next-generation novel and multifunctional optoelectronic devices. Until now, the figure of merits for negative photodetectors, such as responsivity and response speed, still exhibit unsatisfactory performance when compared to their positive counterparts. In this work, an unique gate voltage-dependent ambipolar-response photodetector based on the ReS2/PdSe2 heterostructure with excellent characteristics are prepared and investigated systematically. The evolution for concentration of hole in PdSe2 by gate voltage and the trap states existed at the surface and interface play a dominant role in the transition of negative to positive response. The negative photoresponse performances in terms of responsivity, external quantum efficiency (EQE), and response speed under 638 nm light illumination, are as high as about 532 A/W, 105%, and as fast as 7.9/8.7 µs, respectively. Meanwhile, the corresponding values of the positive response also reach to ∼10.5 A/W, ∼2069 %, and ∼30 µs, respectively, demonstrating the superiority of this heterostructure at ambipolar response. In addition, a similar phenomenon is also observed at the near-infrared region (980 nm). The discovery of these results signifies a pronounced breakthrough in the field of ambipolar photodetectors, thereby paving the way for future advancements in optoelectronic applications.

Controlled Morphological Growth and Photonic Lasing in Cesium Lead Bromide Microcrystals.

Morphology plays a crucial role in defining the optical, electronic, and mechanical properties of halide perovskite microcrystals. Therefore, developing strategies that offer precise control over crystal morphology during the growth process is highly desirable. This work presents a simple scheme to simultaneously grow distinct geometries of cesium lead bromide (CsPbBr3) microcrystals, including microrods (MR), microplates (MP), and microspheres (MS), in a single chemical vapor deposition (CVD) experiment. By strategically adjusting precursor evaporation temperatures, flux density, and the substrate temperature, we surpass previous techniques by achieving simultaneous yet selective growth of multiple CsPbBr3 geometries at distinct positions on the same substrate. This fine growth control is attributed to the synergistic variation in fluid flow dynamics, precursor substrate distance, and temperature across the substrate, offering regions suitable for the growth of different morphologies. Pertinently, perovskite MR are grown at the top, while MP and MS are observed at the center and bottom regions of the substrate, respectively. Structural analysis reveals high crystallinity and an orthorhombic phase of the as-grown perovskite microcrystals, while persistent photonic lasing manifests their nonlinear optical characteristics, underpinning their potential application for next-generation photonic and optoelectronic devices.

Saturable absorption properties of mixed lead-tin halide perovskites and their application in near-infrared ultrafast lasers

Mixed lead–tin halide perovskites, as highly sensitive materials in the near-infrared region, hold significant potential for optoelectronic device applications. Here, mixed lead–tin halide perovskite saturable absorbers (SAs) have been developed by coupling with the side-polished surfaces of the single-mode fibers and excellent saturable absorption effects of the mixed lead–tin halide perovskite SAs have been demonstrated in the near-infrared region. By constructing the in-gap site assisted carrier transfer mode, the saturation absorption process of the mixed lead–tin halide perovskite SAs can be well explained, in which defects as in-gap sites can help the photon-generated carriers transfer into the conduction band and promote the Pauli-blocking-induced absorption bleaching in the SA. Moreover, ytterbium-doped fiber lasers based on perovskite SAs have been fabricated, and mode-locked operations at 1040 nm are achieved using the mixed lead–tin halide perovskite SA, generating ultra-short pulses with a pulse width of 683 fs, 3 dB bandwidth of 4.88 nm, signal-to-noise ratio exceeding 49.74 dB, and a repetition rate of 3.74 MHz. Our findings demonstrate that the mixed lead–tin halide perovskite SAs have excellent optical modulation capability and promising applications in the field of ultrafast photonics.

Effect of Cr-doping on third-order nonlinear optical properties of nanostructured Zn1-xCrxO thin films for Opto-Electronic device applications

Effect of Cr-doping on third-order nonlinear optical properties of nanostructured Zn1-xCrxO thin films for Opto-Electronic device applications

Synthesis of copper oxide (CuO) via coprecipitation method: Tailoring structural and optical properties of CuO nanoparticles for optoelectronic device applications

Oxide-based nanoparticles have been studied extensively due to their unique optical and passivation properties, which are significantly distinct from those of bulk materials. The present study aimed to synthesize copper oxide nanoparticles through the co-precipitation method. The adequate substitution of sodium hydroxide (NaOH) into CuO is analyzed by different characterizations, i.e., X-ray diffraction (XRD), Scanning Electron Microscope (SEM), UV–visible spectroscopy (UV–visible), Fourier transform infrared (FTIR), and EDX. The X-ray diffraction spectra indicate that the prepared copper oxide nanoparticles were crystalline, nano-sized, and highly pure. The SEM micrographs showed that nanoparticles were spherical at lower contents of NaOH, while at higher contents, agglomeration of nanoparticles occurs, and the grain size changes. The decreased optical bandgap of the nanoparticles was observed due to different concentrations of sodium hydroxide. The crystalline size and strain values were also determined through the Williamson-Hall method. The compressive micro-stain in CuO materials confirms the negative slope value of the line fit in the W–H Plot. From this study, we concluded that synthesized CuO NPs have the potential to combine CuO materials with antireflecting films for improved optical performance in optoelectronic devices, precisely current density properties.

Unraveling lead-free Fr-based perovskites FrQCl3 (Q = Ca, Sr) and their pressure induced physical properties: DFT analysis for advancing optoelectronic performance

A comprehensive study of structural, electronic, elastic, and optical properties of the cubic FrQCl3 (Q = Ca, Sr) perovskite under pressure 0 − 105 GPa has been considered. Interestingly, FrCaCl3 experiences a shift from an indirect to a direct bandgap material at 12 GPa, while FrSrCl3 undergoes the same shift at 10 GPa, rendering these materials more advantageous for application in optoelectronic devices. As pressure rises, the electronic density of states increases near the Fermi level by shifting valence band electrons upward. This leads to a reduction in the bandgap and a shift of the bandgap from the ultraviolet to the visible region. The examination of mechanical properties indicates that FrQCl3 (Q = Ca, Sr) perovskite exhibits significant potential for uses requiring a combination of anisotropic, and ductile behavior. Optical property analysis reveals that with an increase in hydrostatic pressure, dielectric constant's peak of both material shift towards lower photon energy area.

[formula omitted] First-principles calculations of optoelectronic characteristics of [formula omitted]&[formula omitted] doped [formula omitted] for energy renewable devices applications [formula omitted]

This research study investigates the structural and optoelectronic characteristics of Eu3+&Tb3+ doped BaSiO3 for energy renewable device applications, using FPLAW (full potential linear augmented plane wave) technique as applied in WIEN-2k code. The generalized gradient approximation has been utilized as the exchange-correlation functional for electrical and optical characteristic computations with Hubbard correction. Electronic characteristics demonstrate semiconducting nature, with a direct bandgap having a value of 1.1 eV for Eu3+ doped BaSiO3 and shows metallic nature, with bandgap 1.4 eV for Tb3+ doped BaSiO3. BaSiO3 Doped with Eu3+ and Tb3+ absorb ultraviolet photons substantially also reflect photons in infrared and visible wavelengths slightly. Such optical properties could be beneficial in optoelectronic device applications. When we doped the parent material, we observed overlap between the CB (conduction band) and VB (valence band), with many of them crossing near to the Fermi level. In electronic properties, for each doped material. The dielectric constant ε(ω), extinction coefficient K(ω), optical loss L(ω), refractive index n(ω), reflectivity R(ω) and absorption coefficient α(ω) being a function of incident photon energies were calculated to examine optical characteristics. BaSiO3 Doped with Eu3+ and Tb3+ absorb ultraviolet photons substantially also reflect photons in infrared and visible wavelengths slightly. Such optical properties could be beneficial in optoelectronic device applications.

Tension Induced Photoluminescence Enhancement in an Organic Single Crystal.

Organic single crystals possess distinct advantages due to their highly ordered molecular structures, resulting in improved stability, enhanced carrier mobility, and superior optical characteristics. However, their mechanical rigidity and brittleness impede the applications in flexible and wearable optoelectronic devices. Here, photoluminescence (PL) emission from 2,6-diphenylanthracene (DPA) single crystals is studied under tensile strain, which shows PL enhancement by more than two times with a strain of ≈1.42%. Such a tension induced PL enhancement is reversible, exhibiting no clear optical degradations during 100 cycles of bending and recovery processes. Theoretical calculations reveal that the deformation of molecular structure under strain induces a decrease of the dihedral between anthracene and benzene moieties in DPA molecules. Further, the increased molecular conjugation enhances the molecular oscillator strength, leading to the brightened PL emission. Meanwhile, with the decreased dihedral, the molecular vibrations in DPA crystals are suppressed, which can reduce the non-radiative decay rate. In contrast, no tension induced PL enhancement is observed in polycrystalline DPA thin films as the strain can be released via the grain boundaries. This study highlights the superior optical performance of DPA single crystals under strain field, which will provide new possibilities for DPA-based flexible devices.