Advanced Optoelectronics Research Articles

Wafer-scale integration of two-dimensional perovskite oxides towards motion recognition

Two-dimensional semiconductors have shown great potential for the development of advanced intelligent optoelectronic systems. Among them, two-dimensional perovskite oxides with compelling optoelectronic performance have been thriving in high-performance photodetection. However, harsh synthesis and defect chemistry severely limit their overall performance and further large-scale heterogeneous integration. Here, we report the wafer-scale integration of highly oriented nanosheets by introducing a charge-assisted oriented assembly film-formation process and confirm its universality and scalability. The shallow-trap dominance induced by structural optimization endows the device with a distinguished performance balance, including high photosensitivity close to that of single nanosheet units and fast response speed. An integrated ultra-flexible 256-pixel device demonstrates the versatility of material-to-substrate integration and conformal imaging functionality. Moreover, the device achieves efficient recognition of multidirectional motion trajectories with an accuracy of over 99.8%. Our work provides prescient insights into the large-area fabrication and utilization of 2D perovskite oxides in advanced optoelectronics.

Impact of surface-roughness and fractality on electrical conductivity of SnS thin films

Mono- and multi-fractal geometry have been used to explore the surface characteristics of scanning electron microscopy (SEM) micrographs of the SnS films with thicknesses of 100nm (SnS1) to 600nm (SnS4), respectively. For this investigation, the SnS thin films have been grown on fluorine-doped tin oxide (FTO)-coated glass substrate through the thermal evaporation route, and surface morphologies are captured by SEM. Two-dimensional multi-fractal detrended fluctuation analysis (MFDFA) based on the partition function is used to examine whether the surfaces have a multi-fractal nature or not. The partition function is applied to extract the generalized Hurst exponent from the segment size. It has been found that surfaces with higher surface roughness induce substantial nonlinearity and a wider width of the multi-fractal spectrum. The multi-fractal spectrum acquired from the analysis of the geometry and shape of the singularity spectrum is used to quantify the irregularity and complexity of surfaces. Minkowski functionals (MFs) parameters such as volume, boundary, and connectivity were measured for each thin film. Moreover, we tried to correlate the electrical conductivity with the mono- and multi-fractal parameters such as fractal dimension (Df), singularity strength function (Δα), singularity spectrum Δf(α), and it is observed that the conductivity of a thin film decreases with decreasing fractal dimension. The minimum (maximum) resistivity (conductivity) was observed for the surface having a larger fractal dimension. The present investigation suggests that such SnS surfaces, having minimal resistivity and maximum conductivity on the roughest surface, indicate enhanced light trapping capacity and can be utilized as active layers for advanced optoelectronics devices.

Giant chiral amplification of chiral 2D perovskites via dynamic crystal reconstruction.

Chiral hybrid perovskites show promise for advanced spin-resolved optoelectronics due to their excellent polarization-sensitive properties. However, chiral perovskites developed to date rely solely on the interaction between chiral organic ligand cations exhibiting point chirality and an inorganic framework, leading to a poorly ordered short-range chiral system. Here, we report a powerful method to overcome this limitation using dynamic long-range organization of chiral perovskites guided by the incorporation of chiral dopants, which induces strong interactions between chiral dopants and chiral cations. The additional interplay of chiral cations with chiral dopants reorganizes the morphological and crystallographic properties of chiral perovskites, notably enhancing the asymmetric behavior of chiral 2D perovskites by more than 10-fold, along with the highest dissymmetry factor of photocurrent (gPh) of ~1.16 reported to date. Our findings present a pioneering approach to efficiently amplify the chiroptical response in chiral perovskites, opening avenues for exploring their potential in cutting-edge optoelectronic applications.

Chirality and magnetic field engineering of linear and quadratic electro-optic properties in Silicene nanotubes for advanced optoelectronic applications

This study provides a comprehensive investigation of the electronic band structure, dipole matrix elements, and optical susceptibility of SiNTs for arbitrary chirality and under the influence of an external magnetic field. Using a tight-binding model including integral hopping up to third-nearest neighbors, the Hamiltonian matrix elements are derived for different SiNT configurations. Results demonstrate that varying the chiral angle of nanotubes effectively tunes the peak positions and intensities of linear optical susceptibility spectra and third-order nonlinear optical susceptibility χ(3)(ω;0,0,ω). This tunability of the optical response, combined with the ability to engineer the peak positions within the visible and near-UV ranges, makes SiNTs potentially useful for a wide range of optoelectronic devices, such as light-emitting diodes (LEDs), photodetectors, and optical modulators.

Unlocking the Potential of Organic-Inorganic Hybrid Manganese Halides for Advanced Optoelectronic Applications.

Organic-inorganic hybrid manganese(II) halides (OIMnHs) have garnered tremendous interest across a wide array of research fields owing to their outstanding optical properties, abundant structural diversity, low-cost solution processibility, and low toxicity, which make them extremely suitable for use as a new class of luminescent materials for various optoelectronic applications. Over the past years, a plethora of OIMnHs with different structural dimensionalities and multifunctionalities such as efficient photoluminescence (PL), radioluminescence, circularly polarized luminescence, and mechanoluminescence have been newly created by judicious screening of the organic cations and inorganic Mn(II) polyhedra. Specifically, through precise molecular and structural engineering, a series of OIMnHs with near-unity PL quantum yields, high anti-thermal quenching properties, and excellent stability in harsh conditions have been devised and explored for applications in light-emitting diodes (LEDs), X-ray scintillators, multimodal anti-counterfeiting, and fluorescent sensing. In this review, the latest advancements in the development of OIMnHs as efficient light-emitting materials are summarized, whichcovers from their fundamental physicochemical properties to advanced optoelectronic applications, with an emphasis on the structural and functionality design especially for LEDs and X-ray detection and imaging. Current challenges and future efforts to unlock the potentials of these promising materials are also envisioned.

Integrated Pristine van der Waals Homojunctions for Self-Powered Image Sensors.

Van der Waals junctions hold significant potentials for various applications in multifunctional and low-power electronics and optoelectronics. The multistep device fabrication process usually introduces lattice mismatch and defects at the junction interfaces, which deteriorate device performance. Here the layer engineering synthesis of van der Waals homojunctions consisting of 2H-MoTe2 with asymmetric thickness to eliminate heterogenous interfaces and thus obtain clean interfaces is reported. Experimental results confirm that the homostructure nature gives rise to the formation of pristine van der Waals junctions, avoiding chemical disorders and defects. The ability to tune the energy bands of 2H-MoTe2 continuously through layer engineering enables the creation of adjustable built-in electric field at the homojunction boundaries, which leads to the achievement of self-powered photodetection based on the obtained 2H-MoTe2 films. Furthermore, the successful integration of 2H-MoTe2 homojunctions into an image sensor with 10 × 10 pixels, brings about zero-power consumption and near-infrared imaging functions. The pristine van der Waals homojunctions and effective integration strategies shed new insights into the development of large-scale application for two-dimensionalmaterials in advanced electronics and optoelectronics.

Defect Engineering of MoTe2 via Thiol Treatment for Type III van der Waals Heterojunction Phototransistor.

Molybdenum ditelluride (MoTe2) nanosheets have displayed intriguing physicochemical properties and opto-electric characteristics as a result of their tunable and small band gap (Eg ∼ 1 eV), facilitating concurrent electron and hole transport. Despite the numerous efforts devoted to the development of p-type MoTe2 field-effect transistors (FETs), the presence of tellurium (Te) point vacancies has caused serious reliability issues. Here, we overcome this major limitation by treating the MoTe2 surface with thiolated molecules to heal Te vacancies. Comprehensive materials and electrical characterizations provided unambiguous evidence for the efficient chemisorption of butanethiol. Our thiol-treated MoTe2 FET exhibited a 10-fold increase in hole current and a positive threshold voltage shift of 25 V, indicative of efficient hole carrier doping. We demonstrated that our powerful molecular engineering strategy can be extended to the controlled formation of van der Waals heterostructures by developing an n-SnS2/thiol-MoTe2 junction FET (thiol-JFET). Notably, the thiol-JFET exhibited a significant negative photoresponse with a responsivity of 50 A W-1 and a fast response time of 80 ms based on band-to-band tunneling. More interestingly, the thiol-JFET displayed a gate tunable trimodal photodetection comprising two photoactive modes (positive and negative photoresponse) and one photoinactive mode. These findings underscore the potential of molecular engineering approaches in enhancing the performance and functionality of MoTe2-based nanodevices as key components in advanced 2D-based optoelectronics.

Enhancement of Photodetector Characteristics by Zn-Porphyrin-Passivated MAPbBr3 Single Crystals.

Perovskite single crystals have garnered significant interest in photodetector applications due to their exceptional optoelectronic properties. The outstanding crystalline quality of these materials further enhances their potential for efficient charge transport, making them promising candidates for next-generation photodetector devices. This article reports the synthesis of methyl ammonium lead bromide (MAPbBr3) perovskite single crystal (SC) via the inverse-temperature crystallization method. To further improve the performance of the photodetector, Zn-porphyrin (Zn-PP) was used as a passivating agent during the growth of SC. The optical characterization confirmed the enhancement of optical properties with Zn-PP passivation. On single-crystal surfaces, integrated photodetectors are fabricated, and their photodetection performances are evaluated. The results show that the single-crystalline photodetector passivated with 0.05% Zn-PP enhanced photodetection properties and rapid response speed. The photoelectric performance of the device, including its responsivity (R), external quantum efficiency (EQE), detective nature (D), and noise-equivalent power (NEP), showed an enhancement of the un-passivated devices. This development introduces a new potential to employ high-quality perovskite single-crystal-based devices for more advanced optoelectronics.

The Interaction of Femtosecond Laser with Perovskites for Advanced Photonics

Halide perovskites have attracted increasingly attention as “rising star” materials for advanced photonics and optoelectronics. Construction micro‐/nano‐architecture of perovskites will provide a good platform to investigate and optimize the fundamental photon–matter–structure interaction. It will also improve the properties, pixelate and miniaturize the integration of versatile optoelectronic devices for emerging applications. In this regard, femtosecond (fs) laser processing technique has been widely used to fabricate micro‐/nano‐architecture with high spatial resolution, limitless flexibility, and unrestricted three‐dimensional structuring capability at a large‐scale, low‐cost way. Concurrently, it is reported that the high refractive index, low thermal conductivity and ultrafast thermalization rate of perovskites are beneficial for the processing by fs laser into micro‐/nano‐architecture without the degradation of their optoelectronic properties. This review systematically summarizes the interaction of fs laser with perovskites, including the mechanisms, and phenomena. Besides the traditional optoelectronics and applications of halide perovskites, the novel properties and applications from optical structures generated by fs laser processing of perovskites are also discussed. The challenges and outlooks for fs laser processed perovskite materials and devices are highlighted. This review will promote the relevant fundamental research on light–matter–structure interaction, and facilitate the integration of perovskite micro‐/nano‐architecture‐based optoelectronic devices.

Deterministic Fabrication and Quantum-Well Modulation of Phase-Pure 2D Perovskite Heterostructures for Encrypted Light Communication.

Deterministic integration of phase-pure Ruddlesden-Popper (RP) perovskites has great significance for realizing functional optoelectronic devices. However, precise fabrications of artificial perovskite heterostructures with pristine interfaces and rational design over electronic structure configurations remain a challenge. Here, the controllable synthesis of large-area ultrathin single-crystalline RP perovskite nanosheets and the deterministic fabrication of arbitrary 2D vertical perovskite heterostructures are reported. The 2D heterostructures exhibit intriguing dual-peak emission phenomenon and dual-band photoresponse characteristic. Importantly, the interlayer energy transfer behaviors from wide-bandgap component to narrow-bandgap component modulated by comprising quantum wells are thoroughly revealed. Functional nanoscale photodetectors are further constructed based on the 2D heterostructures. Moreover, by combining the modulated dual-band photoresponse characteristic with double-beam irradiation modes, and introducing an encryption algorithm mechanism, a light communication system with high security and reliability is achieved. This work can greatly promote the development of heterogeneous integration technologies of 2D perovskites, and could provide a competitive candidate for advanced integrated optoelectronics.

Crafting Near‐Infrared Photonics via the Programmable Assembly of Organic Heterostructures at Multiscale Level

AbstractOrganic single crystals with near‐infrared (NIR) emission demonstrate their excellent optical communications from well photonic confinement and low optical waveguide loss, which are considered as competitive candidates toward advanced optoelectronics. However, the increasingly diverse and sophisticated application demands result in the complicated design of NIR devices, which is hardly realized solely by the intrinsic properties of individual crystals. Herein, a programmable assembly strategy is presented to fabricate organic heterostructures. Triphenylene (TP), pyrene (Py) and 7,7,8,8‐tetracyanoquinodimethane (TCNQ) are primary selected to prepared organic cocrystals with narrow band gap and near‐infrared emission. Importantly, the charge‐transfer alloy with tunable emission from 700 nm to 850 nm and branched heterostructures with multichannel characteristics are prepared from these organic cocrystals by following the growth kinetics process at molecular level and lattice matching principle at structural level, respectively. Theses prepared heterostructures exhibit optical logic operation capabilities, which can serve as optical modulators. This work provides new insights into the manufacturing of organic NIR heterostructures applied in advanced optoelectronics.

Simultaneously Regulated Highly Polarized and Long-Lived Valley Excitons in WSe2/GaN Heterostructures.

Interlayer excitons, with prolonged lifetimes and tunability, hold potential for advanced optoelectronics. Previous research on the interlayer excitons has been dominated by two-dimensional heterostructures. Here, we construct WSe2/GaN composite heterostructures, in which the doping concentration of GaN and the twist angle of bilayer WSe2 are employed as two ingredients for the manipulation of exciton behaviors and polarizations. The exciton energies in monolayer WSe2/GaN can be regulated continuously by the doping levels of the GaN substrate, and a remarkable increase in the valley polarizations is achieved. Especially in a heterostructure with 4°-twisted bilayer WSe2, a maximum polarization of 38.9% with a long lifetime is achieved for the interlayer exciton. Theoretical calculations reveal that the large polarization and long lifetime are attributed to the high exciton binding energy and large spin flipping energy during depolarization in bilayer WSe2/GaN. This work introduces a distinctive member of the interlayer exciton with a high degree of polarization and a long lifetime.

Coherent electronic coupling in quantum dot solids induces cooperative enhancement of nonlinear optoelectronic responses.

Synchronized dynamics of quantum dot (QD) ensembles are essential for generating ultrafast and giant optical responses beyond those of individual QDs. Increasing the strength of the direct electronic coupling between QDs is a key strategy for the realization of cooperative quantum phenomena. Here, we observe a quantum cooperative effect on nonlinear photocurrents caused by the coherent electronic coupling in semiconductor QD solids. We measure quantum interference signals cooperatively generated in QD solids. We control the inter-QD distance with atomic precision using bidentate ligands that strongly link the QDs. The harmonic quantum interference signals are strongly enhanced when shortening the molecular length of the ligand. Furthermore, we clarify that the coherence length of multiexcitons extends to neighbouring QDs. This finding is direct evidence that multiexciton coherent tunnelling assists the ultrafast exciton delocalization. Cooperative enhancement in QD solids may find application in advanced quantum optoelectronics.

All‐Solution‐Processed InGaO/PbI2 Heterojunction for Self‐Powered Omnidirectional Near‐Ultraviolet Photodetection and Imaging

AbstractThe persistent photocurrent (PPC) and high carrier concentration are challenging the ultraviolet photodetection behaviors of amorphous InGaO films. Herein, InGaO/PbI2 heterojunction is constructed by an all‐solution synthesis process to set up a built‐in electric field at the heterojunction interface, which is aimed at the inhibition of PPC, suppression of dark current, and promotion of photogenerated carrier separation. With an optimized In content of 90%, the as‐fabricated InGaO/PbI2 heterojunction photodetector exhibits excellent self‐powered near‐ultraviolet photodetection behaviors with high Ilight/Idark ratio of 104, ultralow dark current of 10−13 A and fast response times of 0.8/0.6 ms. Additionally, benefiting to the all‐solution synthesis process and amorphous characteristic, InGaO/PbI2 heterojunction can be implanted onto any useful substrates to achieve the specific function of photodetection. The as‐fabricated InGaO/PbI2 heterojunction flexible self‐powered photodetector exhibits outstanding mechanical flexibility, bending endurance, and photoelectric stability. When the InGaO/PbI2 heterojunction is implanted onto the transparent substrate, it demonstrates excellent omnidirectional self‐powdered photodetection performance and imaging capability. All results promise all‐solution‐processed InGaO for next‐generation advanced optoelectronics.

Enhancing growth of high-quality two-dimensional CsPbBr3 flakes on sapphire substrate by direct chemical vapor deposition method

Two-dimensional (2D) cesium lead halide (CsPbBr3) nanoflakes have attracted significant attention due to their exceptional optoelectronic properties. Herein, the direct chemical vapor deposition (CVD) method was employed to synthesize high-quality single-crystalline 2D CsPbBr3 flakes on a sapphire substrate using PbBr2 and CsBr precursors. The study offers a comprehensive analysis of the reaction mechanisms involved, including precursor vaporization, transport, decomposition, and subsequent reactions. These factors play a crucial role in modifying the growth process and achieving the desired properties of CsPbBr3 flakes on the sapphire substrate. Additionally, a detailed investigation was conducted into the position-dependent and power-dependent photoluminescence (PL) properties of CsPbBr3flakes on sapphire substrates. The results of this study contribute to the expanding knowledge base regarding the growth of 2D perovskite materials. Moreover, they open up avenues for future research and development in the field of advanced optoelectronics.

Optical and structural properties of bare MoO3 nanobelt, ZnO nanoflakes, and MoO3/ ZnO nanocomposites: The effect of hydrothermal reaction times and molar ratios

In this paper, the successful synthesis of bare molybdenum oxide (MoO3) nanobelts using a one-step hydrothermal method without the use of surfactants is reported. Additionally, ZnO nanoflakes are synthesized through a green method, employing ginger extract, owing to the presence of phenolic compounds found in ginger, mainly gingerols, shogaols, and paradols. Furthermore, the fabrication of MoO3/ZnO nanocomposites using an uncomplicated and readily accessible ultrasonication method is presented. Also, the effects of hydrothermal reaction time (12, 24, and 36 h) and the molar ratio of MoO3 nanobelts (NBs) to ZnO nanoflakes (2:1, 1:1, and 1:2) are investigated on the properties of synthesized MoO3 nanostructures and MoO3/ZnO composites, respectively. The results declare that the optical and structural properties, morphology, and stability of the MoO3 are influenced by hydrothermal reaction time significantly and the uniform MoO3 nanobelts are obtained in a reaction time of 24 h. Also, the formation of nanocomposites with different ratios of MoO3 nanobelt and ZnO nanoflakes by ultrasonication leads to forming uniform distributions of ZnO nanoparticles on the surface of MoO3 structures. Indeed, the ultrasonication condition causes the transformation of the biphasic MoO3 structure to a single-phase MoO3 in the composites. Furthermore, the optical properties of MoO3 nanobelts including the reflection especially in the UV region, and also the bandgap energies of the NBs are affected by providing the nanocomposites, and the bandgap energies change from 2.94 eV (bare MoO3 nanobelts) to 3.18 eV (nanocomposites). The reasons for the phenomena are explained in the paper. These insights into the controlled synthesis of MoO3 nanostructures and MoO3/ZnO nanocomposites pave the way for potential applications in fields such as advanced sensors, optoelectronics, and energy-efficient devices.

Organic Bilayer Heterostructures with Built-In Exciton Conversion for 2D Photonic Encryption.

Organic multilayer heterostructures with accurate spatial organization demonstrate strong light-matter interaction from excitonic responses and efficient carrier transfer across heterojunction interfaces, which are considered as promising candidates toward advanced optoelectronics. However, the precise regulation of the heterojunction surface area for finely adjusting exciton conversion and energy transfer is still formidable. Herein, organic bilayer heterostructures (OBHs) with controlled face-to-face heterojunction via a stepwise seeded growth strategy, which is favorable for efficient exciton propagation and conversion of optical interconnects are designed and synthesized. Notably, the relative position and overlap length ratio of component microwires (LDSA /LBPEA = 0.39-1.15) in OBHs are accurately regulated by modulating the crystallization time of seeded crystals, resulting into a tailored heterojunction surface area (R = Loverlap /LBPEA = 37.6%-65.3%). These as-prepared OBHs present the excitation position-dependent waveguide behaviors for optical outcoupling characteristics with tunable emission colors and intensities, which are applied into two-dimensional (2D) photonic barcodes. This strategy opens a versatile avenue to purposely design OBHs with tailored heterojunctions for efficient energy transfer and exciton conversion, facilitating the application possibilities of advanced integrated optoelectronics.

Improved electrical carrier dynamics and UV detection performance of Zn1-xWxO nanostructured thin films

Current work reports development of Zn1-xWxO nanostructured thin films with Tungsten (W) doping level of 0.0, 1.0, 2.5 and 5.0 wt.% onto glass substrates via successive ionic layer adsorption and reaction (SILAR) method. Films demonstrates improved carrier dynamics and UV photodetection in correlation with W doping level and their suitability in advanced optoelectronics devices. The specimen morphological and structural properties is examined via field emission scanning electron spectroscopy (FESEM) and X-ray diffraction (XRD). In order to understand the electronic structure and carrier dynamics, Raman, UV–Vis, photoluminescence (PL) and time resolve photoluminescence (TRPL) Spectroscopy were employed. Films growth reveals crystallization in hexagonal wurtzite structure and preferred orientation along (002) plane (c-axis). In addition, no phase was observed in diffractograms due to W doping in ZnO matrix. An important effect of W incorporation in ZnO matrix was observed on the grain size and morphology as can be seen in FESEM images. Films optical parameters such as band gap, absorption index and refractive index of films are obtained from absorbance, transmittance and reflectance spectra in UV–Vis-NIR region. The PL spectra of films reveals quenching effect after adding W doping level. The TRPL spectra of films shows that the carrier decay time have been improved with increase in W doping concentrations. On the other hand, films UV detection performance are examined, which reveals significant improvement in response-recovery time, responsivity, external quantum efficiency and detectivity.

Preface to Special Issue on Advanced Optoelectronic and Electronic Devices toward Future Displays

Preface to Special Issue on Advanced Optoelectronic and Electronic Devices toward Future Displays

First-Principles Investigation of Novel Alkali-Based Lead-Free Halide Perovskites for Advanced Optoelectronic Applications.

Lead-free halide perovskites are considered promising candidates as visible light absorbers with outstanding optoelectronic properties. In this work, novel kinds of lead-free halide perovskites were studied for their electronic, optical, and thermoelectric properties by employing the most precise and enhanced modified Trans-Blaha Beck-Johnson potential. The estimated band spectra of the studied materials were comparable. The materials are confirmed to have an indirect band gap semiconducting nature due to the existence of energy band gaps. Among the studied materials, CsSnI3 has a smaller band gap, confirming the excitation to be more energy efficient. Examining the predicted density of states and true electronic orbital contributions, we observed a progressive fluctuation along the energy axis was observed. Furthermore, the linear optical properties are calculated and studied in terms of possible optoelectronic applications. The absorption in KSnI3 was greater compared to the other two materials. The studied materials could be used for antireflecting coatings against UV radiation, owing to the prominent peaks in their reflectivity spectra. The Seebeck coefficient and electrical properties, as well as the positive value of RH all pointed to a p-type nature in these materials. From the anticipated thermoelectric properties, the materials also appear to be suitable for application in thermoelectric devices.