Optoelectronic Devices Research Articles

Band gap engineering and photoelectronic properties of novel pentagonal materials penta-XN2 (X = Ni, Pt): a first principle calculations

Abstract Two-dimensional pentagonal materials as the next-generation nanoelectronic devices are promising candidates due to their interesting structures and novel electronic, mechanical, optical and other properties. Penta-NiN2, a newly synthesized material with pentagonal atomic arrangement under high pressure (ACS Nano 15 (2021), 13 539), has also sparked considerable interest. This study systematically investigates the effects of the biaxial strain on the electronic structure of monolayer penta-NiN2 (penta-PtN2). Furthermore, combining the non-equilibrium Green’s function approach, we research the optoelectronic and transport properties of penta-NiN2 (PtN2). The results indicate that biaxial strain can effectively modulate the bandgap of penta-NiN2 (PtN2), particularly achieving a semiconductor-to-metal transition under compressive strain. Moreover, tensile and compressive strains effectively enhance the optical characteristics of penta-NiN2 (PtN2) in visible light range. Under tensile and compressive strains, the absorption peak of penta-NiN2 shows a red shift and a blue shift in visible region, respectively. The pin-junction photodiode of penta-NiN2 (PtN2) exhibit significant photocurrent under illumination. The strongest photocurrent is observed in penta-NiN2 photodiodes under −3% compressive strain, showing the highest response to yellow light. Under the tensile stress of 7% and compressive stress of −3%, the photocurrent of the Penta-PtN2 photodiode is enhanced in the yellow and green light regions. Additionally, applying compressive strain reduces the bandgap of penta-NiN2 (PtN2), significantly enhancing its transport properties and thereby inducing a switch effect in devices. In summary, our study demonstrates that penta-XN2 (X = Ni, Pt) is a promising material in the fields of nanoelectronics and optoelectronic devices.

Nonlinear Optical Properties of the Topological Material Bi2Se3 Family for the Application of an Ultrafast Pulse Laser Based on the Occupied and Unoccupied Band Structures.

The Bi2Se3 family can exhibit many intriguing topological insulator properties, including a narrow bandgap and strong surface states, which show excellent nonlinear optical properties. Thinning bulk Bi2Se3 family materials to create a low-cost photoelectric modulation device and explaining the mechanisms of nonlinear optical differences in different types of materials remain challenges. Based on liquid-phase exfoliation technology and tapered fiber, this work prepared optoelectronic modulation devices for various samples within the Bi2Se3 family, quantitatively compared their nonlinear optical properties, and analyzed the sources of differentiation using the occupied and unoccupied multiband structure theory. The results correspond well to the phenomena observed in the ultrafast laser, which will provide strong support for the design of higher performance photoelectric devices based on topological insulators.

Unleashing the nonlinear optical response of layered vanadium diselenide towards the deep mid-infrared regime

Broadband nonlinear optical materials towards the deep mid-infrared regime are highly required in medical diagnostics, environmental pollution monitoring, etc. Here, we report the ultra-broadband nonlinear optical absorption behavior of the layered vanadium diselenide (VSe2) towards deep mid-infrared regime experimentally. The layered VSe2 prepared by the liquid-phase exfoliation method exhibits broadband and wavelength-dependent nonlinear saturable absorption and a large modulation depth of over 8% in the 3-10 µm spectral range. By utilizing the layered VSe2 for optical modulation, stable nanosecond pulse with a low Q-switched threshold has been delivered successfully from an erbium-doped ZBLAN fiber laser. The experimental findings can deepen the understanding of the nonlinear optical response of the transition metal dichalcogenides towards the deep mid-infrared regime, and may make inroads for the advancement of mid-IR optoelectronic devices.

Atomic Layer Deposition of ZnO on CsPbBr3 Perovskite Nanocrystals: Surface-Dependent Mechanistic Insights.

In this study, we investigate the atomic layer deposition (ALD) process on all-inorganic CsPbBr3 perovskite nanocrystals (PNCs) to introduce an inorganic electron transport layer (ETL) in light-emitting diode (LED) devices. Two types of CsPbBr3 PNCs were synthesized with oleate (OA) and oleylammonium (OLA) ligands on the surface. We found that CsPbBr3 PNCs with Cs oleate surfaces experienced severe photoluminescence (PL) quenching after the ALD process, while those with oleylammonium bromide surfaces did not show any significant PL drop. Transmission electron microscopy and X-ray photoelectron spectroscopy revealed that significant Pb metal formation and Ruddlesden-Popper planar faults, linked to uncoordinated Pb2+ ion defects, were generated in CsPbBr3 PNCs terminated with Cs oleate after ALD ZnO. Finally, we fabricated LEDs using PNCs with an ALD ZnO process to introduce inorganic ZnMgO nanoparticles as the ETL. The devices processed with ALD exhibited superior luminance and external quantum efficiency compared to those without the ALD process. This research provides crucial insights into the surface-dependent chemistry of PNCs and the surface-dependent performance of perovskite-based optoelectronic devices.

Effects of ion irradiation induced phase transformations and oxygen vacancies on the leakage current characteristics of HfO2 thin films deposited on GaAs

Abstract We report on the ion-induced phase transformations, defect dynamics related to oxygen vacancies and the resulting leakage current characteristics of RF sputtered HfO2 thin films grown on GaAs. A systematic growth of HfO2 grains and Ion prompted phase transformations of HfO2 to crystalline phases such as monoclinic and tetragonal/orthorhombic (mixed phase) in otherwise amorphous HfO2 thin films have been observed after irradiation. At lower fluences, Ion induced enhancement in the dielectric properties of HfO2 thin films resulted in a reduction in the leakage current, whereas ion prompted defect formation at higher fluences caused a systematic increase in the leakage current density. Further, the effects of Poole-Frenkel (PF) tunneling and Fowler-Nordheim (FN) tunneling on the leakage current have also been investigated. These mechanisms showed the existence of impurities in the as-grown films. Photoluminescence (PL) study suggests the variation in the defect configuration related to O-vacancies and slight shift in the peak positions due to SHI irradiation are responsible for the observed changes in electrical characteristics. This study offers worthwhile information for considering the effects of electronic excitation prompted defect annealing or defect creation on the performance of HfO2/GaAs based photonic and optoelectronic devices, particularly, when such devices are operated in a radiation harsh environment.

First-Principles Investigation of Structural, Electronic, Optical, Elastic, and Thermoelectric Properties of Cubic Francifluorite Perovskites FrXF3 (X = Si, Ge, and Sn) for Optoelectronic and Thermoelectric Device Applications

Abstract This study presents the results of first-principles calculations based on Density Functional Theory (DFT) implemented in the Wien2k code, investigating the properties of FrXF3 compounds where B represents Si, Ge, and Sn. Various exchange-correlation functionals, including Generalized Gradient Approximation (GGA) with Perdew-Burke-Ernzerhof (GGA-PBE), Perdew-Burke-Ernzerhof revised for Solids (GGA-PBEsol), Wu-Cohen exchange (GGA-WC), and Modified Becke-Johnson potential (TB-mBJ), were employed to comprehensively analyze the structural, electronic, optical, elastic, and thermoelectric characteristics of these compounds. The analysis of band structures and density of states revealed that all three compounds exhibit semiconducting behavior with direct band gaps, and the band gaps decrease as we move from Si to Sn. The calculated optical properties indicate strong optical responses in the visible to ultraviolet energy range, suggesting potential applications in optoelectronics. Furthermore, the study evaluated the thermoelectric parameters, including thermal and electrical conductivity, power factor, Seebeck coefficient, and figure of merit. The results demonstrate that the FrXF3 compounds possess remarkable thermoelectric potential, indicating their suitability for thermoelectric applications. Overall, this comprehensive investigation provides valuable insights into the structural, electronic, optical, elastic, and thermoelectric properties of FrXF3 compounds, highlighting their potential for various technological applications, particularly in the field of optoelectronics and thermoelectric devices.

Photoinduced charge transfer and excitonic energy transfer in the CuInS2/ZnS/MoS2 heterotrilayer

Photo-induced charge transfer is the key process of many applications such as photovoltaics, photodetection, and light-emitting devices. With the outgrowth of a new class of low-dimensional semiconductors, i.e., monolayer transition metal dichalcogenides and semiconductor nanocrystals, charge transfer at the 2D/0D heterostructures has drawn many efforts because of the outstanding optical and electrical properties. This paper studies the dynamics of excitons of the CuInS2/ZnS/MoS2 heterotrilayer through femtosecond time-resolved transient absorption spectroscopy. The electron and hole transfer are observed by selectively exciting the electrons with tunable pump wavelengths. The exciton lifetimes are obtained on the picosecond scale. This work provides clues on exploring the non-toxic optoelectronic devices based on the CuInS2/ZnS/MoS2 heterotrilayer.

Zipper‐Like Dynamic Switching of Coordination Bonds Gives a Polar Bimetallic Halide Toward Self‐Driven X‐Ray Detection

AbstractPolar molecular crystals hold a promise for controlling bulk physical properties originated in their unique switchable polarity via structural transformation. However, the mechanisms for switching polarization are mainly limited to displacive and disorder‐order phase transitions, which rarely involve the reconstruction of chemical bonds. Here, we have switched and tuned electric polarization in a bimetallic halide, (Neopentylammonium)4AgBiBr8 (1), as verified by light‐excited pyroelectric effect. Most notably, its Ag−Br coordination bonds show a zipper‐like dynamic switching behavior from the ‘locked’ to ‘unlocked’ state, namely, reconstruction of chemical bonds. Coupling with the dynamic ordering of organic cations, this bond‐switching transition makes a contribution to switchable polarization of 1. As expected, its polarity creates pyroelectric effect for self‐driven X‐ray detection with high sensitivity (3.8×103 μC Gy−1 cm−2) and low limit of detection (4.8 nGy s−1). This work on the bond‐switching mechanism provides an avenue to design polar molecular candidate for smart optoelectronic devices.

Regulating Optoelectronic and Thermoelectric Properties of Organic Semiconductors by Heavy Atom Effects

AbstractHeavy atom effects can be used to enhance intermolecular interaction, regulate quinoidal resonance properties, increase bandwidths, and tune diradical characters, which have significant impacts on organic optoelectronic devices, such as organic field‐effect transistors (OFETs), organic light‐emitting diodes (OLEDs), organic photovoltaics (OPVs), etc. Meanwhile, the introduction of heavy atoms is shown to promote charge transfer, enhance air stability, and improve device performances in the field of organic thermoelectrics (OTEs). Thus, heavy atom effects are receiving more and more attention. However, regulating heavy atoms in organic semiconductors is still meeting great challenges. For example, heavy atoms will lead to solubility and stability issues (tellurium substitution) and lack of versatile design strategy and effective synthetic methods to be incorporated into organic semiconductors, which limit their application in electronic devices. Therefore, this work timely summarizes the unique functionalities of heavy atom effects, and up‐to‐date progress in organic electronics including OFETs, OPVs, OLEDs, and OTEs, while the structure‐performance relationships between molecular designs and electronic devices are clearly elucidated. Furthermore, this review systematically analyzes the remaining challenges in regulating heavy atoms within organic semiconductors, and design strategies toward efficient and stable organic semiconductors by the introduction of novel heavy atoms regulation are proposed.

Zipper-Like Dynamic Switching of Coordination Bonds Gives a Polar Bimetallic Halide Toward Self-Driven X-Ray Detection.

Polar molecular crystals hold a promise for controlling bulk physical properties originated in their unique switchable polarity via structural transformation. However, the mechanisms for switching polarization are mainly limited to displacive and disorder-order phase transitions, which rarely involve the reconstruction of chemical bonds. Here, we have switched and tuned electric polarization in a bimetallic halide, (Neopentylammonium)4AgBiBr8 (1), as verified by light-excited pyroelectric effect. Most notably, its Ag-Br coordination bonds show a zipper-like dynamic switching behavior from the 'locked' to 'unlocked' state, namely, reconstruction of chemical bonds. Coupling with the dynamic ordering of organic cations, this bond-switching transition makes a contribution to switchable polarization of 1. As expected, its polarity creates pyroelectric effect for self-driven X-ray detection with high sensitivity (3.8×103 μC Gy-1 cm-2) and low limit of detection (4.8 nGy s-1). This work on the bond-switching mechanism provides an avenue to design polar molecular candidate for smart optoelectronic devices.

Thickness-dependent nanoscale friction across the first-order charge density wave phase transition in 1T-TaS2

The layered charge density wave (CDW) phase transition material 1T-TaS2 has garnered significant attention due to its modulable bandgap and electrical transport properties. These unique properties make 1T-TaS2 highly promising for applications in fields such as optoelectronic devices and microstructure physics devices. In various micro-/nanodevices made from quasi-two-dimensional 1T-TaS2, it is often utilized in thin layers, making the understanding of its frictional properties crucial for practical applications. However, the layer-dependent frictional properties of 1T-TaS2 have not been thoroughly investigated. In this article, we examine the CDW phase transition between the nearly commensurate (NCCDW) and commensurate (CCDW) phases in 1T-TaS2 around 183 K using atomic force microscopy, focusing on the number of layers in the samples. Our results indicate that for thicker samples with more than approximately 17 layers, a friction peak is observed during the NCCDW–CCDW phase transition. In contrast, thinner samples do not exhibit this friction peak, and their friction continuously increases as the temperature decreases. This behavior is attributed to the suppressed NCCDW–CCDW phase transition in thinner samples. These results enhance our understanding of the frictional behavior of 1T-TaS2 in the context of micro-/nano-electromechanical systems. Furthermore, our observations offer a straightforward method to identify the NCCDW–CCDW phase transition, providing an alternative to traditional, more complex techniques such as electrical resistance measurements and Raman spectroscopy.

Polypyrrole-bismuth tungstate/polypyrrole core-shell for optoelectronic devices exhibiting Schottky photodiode behavior

Polypyrrole-bismuth tungstate/polypyrrole core-shell for optoelectronic devices exhibiting Schottky photodiode behavior

Advances in Organic Materials for Next-Generation Optoelectronics: Potential and Challenges

This review provides a comprehensive overview of recent advancements in the synthesis, properties, and applications of organic materials in the optoelectronics sector. The study emphasizes the critical role of organic materials in the development of state-of-the-art optoelectronic devices such as organic solar cells, organic thin-film transistors, and OLEDs. The review further examines the structure, operational principles, and performance metrics of organic optoelectronic devices. Organic materials have emerged as promising candidates due to their low-cost production and potential for large-area or flexible substrate applications. Additionally, this review highlights the physical mechanisms governing the optoelectronic properties of high-performance organic materials, particularly photoinduced processes relevant to charge carrier photogeneration. It discusses the unique benefits of organic materials over traditional inorganic materials, including their light weight, simple processing, and flexibility. The report delves into the challenges related to stability, scalability, and performance, while highlighting the wide range of electronic properties exhibited by organic materials, which are critical for their performances in optoelectronic devices. Furthermore, it addresses the need for further research and development in this field to achieve consistent performance across different types of devices.

2D/3D Heterostructure Halide Perovskite Thin Films through an Innovative Spray‐Deposition of Bulky Organic Cation‐Containing Ammonium Salts

AbstractHybrid halide perovskite involving low‐dimensional (2D or quasi‐2D) perovskites and their three‐dimensional (3D) counterparts provide long‐term stability in solar photovoltaics (PV) applications. Besides stability, perovskite PV commercialization would scalability in roll‐to‐roll fabrication of large‐area devices. Herein, it is reported on a pneumatic spray‐deposition methodology utilized to fabricate 2D/3D heterostructure perovskite films with tunable morphological and optical properties. Ammonium salts featuring bulky organic cations, such as phenethylammonium iodide (PEAI), 2‐thiophenemethylammonium iodide (TMAI), cyclohexylmethylammonium iodide (CMAI), and n‐dodecylammonium iodide (DDAI) are spray‐deposited on top of 3D‐formamidinium lead triiodide (3D‐FAPbI3) perovskite thin films, to synthesize a series of 2D perovskites, including (PEA)2FAPb2I7, (TMA)2PbI4, (CMA)2FAPb2I7, and (DDA)2FAPb2I7. X‐ray diffraction (XRD) and grazing incidence wide‐angle X‐ray scattering measurements confirm the evolution of 2D perovskite layer with distinct crystal structure and dimensionality (n = 1 and 2). Additionally, field‐emission scanning electron microscopy reveals diverse surface morphologies achievable in the 2D perovskite layers. Hyperspectral photoluminescence mapping further demonstrates that the emission at ≈566–570 nm corresponds exclusively to the 2D perovskite phase with n = 2. This study advances the development of 2D/3D heterostructure perovskites using bulky organic cations and underscores the potential of pneumatic spray‐deposition as a scalable fabrication technique for producing next‐generation optoelectronic devices.

Electronic properties of corundum-like Ir2O3 and Ir2O3-Ga2O3 alloys

In the hexagonal, corundum-like structure, α-Ga2O3 has a bandgap of ∼ 5.1 eV, which, combined with its relatively small electron effective mass, high Baliga's figure of merit, and high breakdown field, makes it a promising candidate for power electronics. Ga2O3 is easy to dope n-type, but impossible to dope p-type, impeding the realization of some electronic device designs. Developing a lattice-matched p-type material that forms a high-quality heterojunction with n-type Ga2O3 would open new opportunities in electronics and perhaps optoelectronic devices. In this work, we studied Ir2O3 as a candidate for that purpose. Using hybrid density functional theory calculations we predict the electronic band structure of α-Ir2O3 and compare that to α-Ga2O3, and study the stability and electronic properties of α-(IrxGa1−x)2O3 alloys. We discuss the band offset between the two materials and compare it with recently available experimental data. We find that the Ir d bands that compose the top of the valence band in α-Ir2O3 are much higher in energy than O p bands in α-Ga2O3, possibly enabling effective p-type doping. Our results provide an insight into using the Ir2O3 or Ir2O3-Ga2O3 alloys as p-type material lattice-matched to α-Ga2O3 for the realization of p–n heterojunctions.

Piezoelectric dispenser printing and intense pulsed light sintering of AgNW/PEDOT:PSS hybrid transparent conductive films

A hybrid transparent conductive films (TCFs) combining silver nanowires (AgNWs) and poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) was fabricated using a piezoelectric dispenser printing method. The innovation lies in optimizing the ink composition and employing intense pulsed light sintering to enhance the TCF's performance. The optimized AgNW/PEDOT:PSS mixture, with an 8:2 ratio, achieved a figure of merit (FOM) of 28.05 × 10-3Ω-1, corresponding to a sheet resistance of 9.93 Ω sq-1and a transmittance of 88.0%. This represents a significant improvement over the pre-sintering FOM of 24.09 × 10-3Ω-1. Additionally, the hybrid TCFs exhibited outstanding structural stability, maintaining functionality after 7000 mechanical bending cycles. The results enable applications in flexible optoelectronic devices, and highlight the potential of this method to produce high-performance, flexible, and durable transparent electrodes, advancing the development of next-generation optoelectronic devices.

Perspective of environmentally friendly antimony selenide-based solar cell

Antimony selenide has been intensively investigated as an interesting alternative for solar cell absorbers due to its excellent physical properties. Owing to the remarkable advancements in the last several decades, chemical and physics methods have improved the power conversion efficiency of antimony selenide solar cells by over 10%, almost at the level needed for industrial applications. In this perspective, we have outlined the issues and challenges these antimony chalcogenides face in photoelectric applications. We have proposed some feasible suggestions for improving its performance and applications in solar cells and other optoelectronic devices.

Low temperature exciton lifetime enhancement of MAPbBr3 studied by broadband terahertz spectroscopy

Over the past few years, lead halide perovskites have demonstrated significant potential in the field of solar cells, light-emitting diodes, and field-effect transistors. We investigated the transient photoconductivity and temperature-induced phase transitions in MAPbBr3 thin films, using ultrabroadband optical pump-terahertz probe spectroscopy with varying excitation fluences and temperature conditions. As the temperature drops from 293 to 123 K, MAPbBr3 undergoes two phase transitions, resulting in a significant extension of exciton lifetime in the tetragonal phase near 150 K, where MAPbBr3 exhibits a longer exciton lifetime. Our research contributes to a better understanding of the temperature-induced phase transition mechanism of MAPbBr3, enhancing its potential applications in optoelectronic devices.

Impact of metal deposition on the optical and interface properties of NiO: growth and characterization of NiO/metal thin bilayer films

Abstract Since transparent conductive oxides (TCOs) provide electrical conductivity together with optical transparency, they have found wide applications in optoelectronic devices and photovoltaics. Among the TCOs, nickel oxide (NiO) is challenging due to its inherent trade-off between transparency and electrical conductivity. To address this challenge, one effective approach is to deposit a metal layer onto NiO thin films. In this work, NiO, NiO/Au, NiO/Ag, and NiO/Cu thin films are prepared by sputtering and thermal evaporation techniques on glass substrates and fully characterized finding the proper film for optoelectronic applications. The electrical and optical properties of the fabricated films are examined by four-point probe measurements and optical spectrometry. According to the obtained results, the NiO/Au, NiO/Ag, and NiO/Cu bilayers show sheet resistance of 200, 338, and 925 Ω sq−1 respectively while their optical bandgaps vary from 3.2 to 3.76 eV. These findings provide valuable insights into the performance of these films, making them potentially viable choices for various optoelectronic applications.

A VOx-based optoelectronic memristor for application in visual perception

Abstract While biological vision systems excel at in-memory processing with low power consumption, traditional silicon-based vision chips struggle with high energy demands. This gap motivates the exploration of alternative materials for artificial intelligence applications. This paper presents a VOx-based optoelectronic synaptic memristive device. The proposed artificial synaptic device ITO/VO x /Pt mimics biological functions such as potentiation (P), depression (D), long-term memory, short-term memory (STM), and paired-pulse facilitation (PPF). The PPF index, standing at 105%, suggests a favorable pattern in STM function. The device served as synapses within a spiking neural network showing an achievable pattern classification accuracy of 88.68%, highlighting the potential of the VO x synaptic device for pattern classification tasks. The suggested VO x -based synaptic devices could represent an efficient pattern recognition and visual perception application.