Range Of Applications In Optoelectronic Devices Research Articles

Large lateral photovoltaic effect with ultrafast optical relaxation time in SnS2/n-Si junctions.

A large lateral photovoltaic effect (LPE) with a fast optical response time is necessary to develop high-performance position-sensitive detectors. In this paper, we report an LPE with a high self-powered position sensitivity and ultrafast optical relaxation time in S n S 2/n-S i junctions prepared using pulsed laser deposition. A large built-in electric field was generated at the S n S 2/S i interface, which resulted in a large LPE with a positional sensitivity of up to 116mV/mm. Furthermore, the measurement circuit with multiple parallel resistors had a strong influence on the ultrafast optical response time of the LPE and the fastest optical relaxation time observed was ∼0.44µs. Our results suggest that the S n S 2/S i junction would be a promising candidate for a wide range of optoelectronic device applications.

Influence of SWCNT on the Electrical Behavior of an Environmentally Friendly CH3NH3SnI3 Perovskite-Based Optoelectronic Schottky Device

The lead-free tin-based halide perovskite CH3NH3SnI3 has recently been explored in a wide range of optoelectronic device applications. However, the charge conduction process of the CH3NH3SnI3 perovskite layer is hindered by the presence of vacancies resulting from tin oxidation, sample defects, and trap states, which limit the performance of the device. In this study, we introduced single-walled carbon nanotubes (SWCNTs) into the perovskite to enhance the charge conduction of the device. To demonstrate this, CH3NH3SnI3 perovskite and its composites with SWCNTs were synthesized and used as an active layer in a sandwich-structured device. Electrical measurements show that the device based on SWCNTs exhibits superior performance compared to the device consisting solely of perovskite. Incorporating SWCNTs into the device improves conductivity and reduces series resistance. Specifically, in the absence of light, SWCNTs increase the conductivity from 3.8 × 10–5 to 1.6 × 10–4 S/m and decrease the series resistance from 348.25 to 34.80 Ω. Under illumination, SWCNTs further increase conductivity to 4.0 × 10–4 S/m from 8.1 × 10–5 S/m and decrease series resistance to 19.20 Ω from 220.56 Ω. The results suggest that SWCNT can serve as a channel for charge extraction. An analysis of space charge limited current (SCLC) conduction indicates that incorporating SWCNT decreases the trap energy from 103.22 to 79.70 meV under dark conditions. This implies that SWCNT also acts as a filler for trap states. Based on these findings, it appears that the SWCNT-CH3NH3SnI3 perovskite composite has the potential to yield high-performance optoelectronic devices. This study presents an intriguing approach for enhancing carrier transfer with minimal recombination loss and could serve as a source of inspiration for future research in the optoelectronics field.

Recombination radiation of heteroepitaxial structures with InAs quantum dots grown on surface of (311)B GaAs by MBE

Dynamics of recombination radiation is found to be fundamental for control the efficiency of quantum dots (QDs) based structures for different range of optoelectronic device applications. We presented results of an experimental study of recombinational radiation of heteroepitaxial strongly confined InAs QD structures with s which are grown up on a surface of the semi-insulating (311)B GaAs substrate by molecular beam epitaxy. It is shown that for the InAs QDs dots, with characteristic dimensions of 12 x 6 nm2, half-width (FWHM) of the observed recombination line attributed to the main electronic fundamental transition of the exciton at 1.1690 meV at T = 77 K is 41.58 meV. This value of FWHM is substantially less than typical literature values obtained under comparable experimental conditions for heteroepitaxial structures with InAs QDs, grown on vicinal surfaces of (100) GaAs substrate with angle of disorientation 7° relative to direction [001].

Structural and Optical Studies of Synthesized Semiconductor NixZn1-xS Nanostructure Thin Films for Optoelectronic Device Applications

Transition metal ions like Nickel doped ZnS semiconductor materials have a wide range of optoelectronic device applications. However, the doping concentration effect on the properties of NixZn1-xS has not been reported. This study, therefore, investigated the effects of nickel (Ni) doping concentration on the structural and optical properties of synthesized NixZn1-xS nanostructured thin films prepared by low-cost Chemical Spray Pyrolysis (CSP) technique. NixZn1-xS nanostructured thin films with a thickness of 320nm and different mole ratios (𝑥 = 0.00, 0.02, 0.04, 0.06 and 0.08,) were grown by the use of spray solution on hot glass substrates at a temperature of 300oC using CSP technique. The spray solutions contain nickel acetate, zinc acetate, and thiourea as precursors for Nickel, Zinc, and Sulphur, respectively. The influence of Ni doping concentration on the structural, optical, and morphological properties were investigated using X-ray diffraction (XRD), Ultraviolet-Visible spectroscopy (UV-vis) and Scanning Electron Microscopy (SEM) respectively. The XRD analysis indicated that all the prepared films retained the ZnS cubic zinc blend structure. SEM results show that the films are composed of well crystalline grains with various shapes and densely bound to each other. The UV-vis spectroscopy shows that transmittance is moderately high and increased with increasing Ni content. The average transmittance of NixZn1-xS are 61.3%, 62.8%, 63.9%, 67.6 and 69.6% for x = 0.00, 0.02, 0.04, 0.06 and 0.08, respectively. The bandgap of Ni-doped ZnS samples is low compared to the undoped, and the value increases gradually with increasing Ni concentration. Based on the results obtained, with the enhanced structural and optical properties, NixZn1-xS films could be a useful material in the future of optoelectronic applications.

Investigation of light-matter interaction in single vertical nanowires in ordered nanowire arrays.

Quasi one-dimensional semiconductor nanowires (NWs) in either arrays or single free-standing forms have shown unique optical properties (i.e., light absorption and emission) differently from their thin film or bulk counterparts, presenting new opportunities for achieving enhanced performance and/or functionalities for optoelectronic device applications. However, there is still a lack of understanding of the absorption properties of vertically standing single NWs within an array environment with light coupling from neighboring NWs within certain distances, due to the challenges in fabrication of such devices. In this article, we present a new approach to fabricate single vertically standing NW photodetectors from ordered InP NW arrays using the focused ion beam technique, to allow direct measurements of optical and electrical properties of single NWs standing in an array. The light-matter interaction and photodetector performance are investigated using both experimental and theoretical methods. The consistent photocurrent and simulated absorption mapping results reveal that the light absorption and thus photoresponse of single NWs are strongly affected by the NW array geometry and related light coupling from their surrounding dielectric environment, due to the large absorption cross section and/or strong light interaction. While the highest light concentration factor (∼19.64) was obtained from the NW in an array with a pitch of 1.5 μm, the higher responsivity per unit cell (equivalent to NW array responsivity) of a single vertical NW photodetector was achieved in an array with a pitch of 0.8 μm, highlighting the importance of array design for practical applications. The insight from our study can provide important guidance to evaluate and optimize the device design of NW arrays for a wide range of optoelectronic device applications.

P-Type transparent Cu2S thin film grown by Thermionic Vacuum Arc for optoelectronic applications

In this study, we have used a new single-step method for producing Cu2S thin films, which have good transparency in the visible range and high hole conductivity properties suitable for a wide range of optoelectronic device applications. Cu2S thin films are deposited by the Thermionic Vacuum Arc method, which is capable of very high deposition rates with high uniformity. The structural properties were determined by XRD analysis, and the morphological features were examined by AFM and SEM techniques. From XRD studies, the thin films were found to have a nano-crystalline form. The morphology images showed that the thin films have very low surface roughness. The bandgap of the film was calculated. The electrical properties of the films such as resistivity, majority carrier, and concentration were determined by Hall Effect measurements. In addition, the figure of merit value was calculated for p-type Cu2S transparent conducting thin films using the Haacke’s formula.

P to n-type transition with wide blue shift optical band gap of spray synthesized Cd doped CuO thin films for optoelectronic device applications

CuO thin film has a wide variety of potential applications due to distinctive optical properties and native p-type electrical conductivity. The weak p-type electrical conductivity of CuO thin film can be modified via doping suitable elements into it. In this work, we acquired n-type electrical conductivity in the CuO thin film by cadmium (Cd) doping for the first time. Pristine and Cd doped CuO thin films are fabricated at 325 ºC using a simple spray pyrolysis technique with different doping concentrations (i.e. x = 0.00, 0.02, 0.04, 0.06 and 0.08). X-ray diffraction (XRD) spectra of Cd doped CuO thin films match to the polycrystalline with a monoclinic structure and no peak corresponding to Cd impurity or non-stoichiometric phases are found in the XRD pattern. Based on the XRD patterns, the average crystallite size is obtained from 15.12 to 30.53 nm. Furthermore, a closely-spaced nanoparticle is confirmed by the field emission scanning electron microscopes (FESEM). The energy dispersive analysis X-ray spectra (EDAX) demonstrate the effect of substitutions of Cu2+ ions by Cd2+ ions in the pristine CuO lattice network. Hall Effect measurements reveal that the p-type conductivity of CuO thin films alters to n-type as a result of Cd doping. The electrical resistivity of Cd doped CuO thin films upraise with the reduction of carrier concentration and increment of carrier mobility with the increase of Cd concentration in the films. An increment of transmittance and broadening of the blue shift optical band gap is possessed in CuO thin films via Cd doping and found as a promising material for a wide range of optoelectronic device applications.

Ultrahigh position sensitivity and fast optical relaxation time of lateral photovoltaic effect in Sb2Se3/p-Si junctions.

A large lateral photovoltaic (LPV) effect with good linearity and fast response time is necessary for developing high-performance position-sensitive detectors (PSD). In this paper, we investigated the influence of the resistance of Sb2Se3 film and the Si on the LPV properties of the Sb2Se3/p-Si junctions. The LPV exhibits a linear dependence on the laser spot position, with a maximum position sensitivity as high as 448 mV/mm. The optical relaxation time of the LPV was about 4.98 μs, which was due to the formation of the inversion layer at the Sb2Se3/p-Si interface. Our results revealed that the high resistivity of Sb2Se3 film facilitate the LPV and confirmed the resistivity of Si substrate play a key role in the LPV properties. The giant position sensitivity and fast relaxation times of the LPV suggest that the Sb2Se3/p-Si junction is a promising candidate for a wide range of optoelectronic device applications.

Biexciton Resonances Reveal Exciton Localization in Stacked Perovskite Quantum Wells.

Quasi-two-dimensional lead halide perovskites, MAn-1PbnX3n+1, are quantum confined materials with an ever-developing range of optoelectronic device applications. Like other semiconductors, the correlated motion of electrons and holes dominates the material's response to optical excitation influencing its electrical and optical properties such as charge formation and mobility. However, the effects of many-particle correlation have been relatively unexplored in perovskite because of the difficultly of probing these states directly. Here, we use double quantum coherence spectroscopy to explore the formation and localization of multiexciton states in these materials. Between the most confined domains, we demonstrate the presence of an interwell, two-exciton excited state. This demonstrates that the four-body Coulomb interaction electronically couples neighboring wells despite weak electron/hole hybridization in these materials. Additionally, in contrast with inorganic semiconductor quantum wells, we demonstrate a rapid decrease in the dephasing time as wells become thicker, indicating that exciton delocalization is not limited by structural inhomogeneity in low-dimensional perovskite.

Improved Electrical Conductivity of Graphene Films Integrated with Metal Nanowires

Polycrystalline graphene grown by chemical vapor deposition (CVD) on metals and transferred onto arbitrary substrates has line defects and disruptions such as wrinkles, ripples, and folding that adversely affect graphene transport properties through the scattering of the charge carriers. It is found that graphene assembled with metal nanowires (NWs) dramatically decreases the resistance of graphene films. Graphene/NW films with a sheet resistance comparable to that of the intrinsic resistance of graphene have been obtained and tested as a transparent electrode replacing indium tin oxide films in electrochromic (EC) devices. The successful integration of such graphene/NW films into EC devices demonstrates their potential for a wide range of optoelectronic device applications.