Diverse Optoelectronic Applications Research Articles

Reversible chirality inversion of an AuAgx-cysteine coordination polymer by pH change

Responsive chiral systems have attracted considerable attention, given their potential for diverse applications in biology, optoelectronics, photonics, and related fields. Here we show the reversible chirality inversion of an AuAgx-cysteine (AuAgx-cys) coordination polymer (CP) by pH changes. The polymer can be obtained by mixing HAuCl4 and AgNO3 with L-cysteine (or D-cysteine) in appropriate proportions in H2O (or other surfactant solutions). Circular dichroism (CD) spectrum is used to record the strong optical activity of the AuAg0.06-L-cys enantiomer (denoted as L0.06), which can be switched to that of the corresponding D0.06 enantiomer by alkalization (final dispersion pH > 13) and can be switched back after neutralization (final dispersion pH <8). Multiple structural changes at different pH values (≈9.6, ≈13) are observed through UV-Vis and CD spectral measurements, as well as other controlled experiments. Exploration of the CP synthesis kinetics suggests that the covalent bond formation is rapid and then the conformation of the CP materials would continuously evolve. The reaction stoichiometry investigation shows that the formation of CP materials with chirality inversion behavior requires the balancing between different coordination and polymerization processes. This study provides insights into the potential of inorganic stereochemistry in developing promising functional materials.

Density Functional Theory Unveils the Secrets of SiAuF3 and SiCuF3: Exploring Their Striking Structural, Electronic, Elastic, and Optical Properties.

In the quest for advanced materials with diverse applications in optoelectronics and energy storage, we delve into the fascinating world of halide perovskites, focusing on SiAuF3 and SiCuF3. Employing density functional theory (DFT) as our guiding light, we conduct a comprehensive comparative study of these two compounds, unearthing their unique structural, electronic, elastic, and optical attributes. Structurally, SiAuF3 and SiCuF3 reveal their cubic nature, with SiCuF3 demonstrating superior stability and a higher bulk modulus. Electronic investigations shed light on their metallic behavior, with Fermi energy levels marking the boundary between valence and conduction bands. The band structures and density of states provide deeper insights into the contributions of electronic states in both compounds. Elastic properties unveil the mechanical stability of these materials, with SiCuF3 exhibiting increased anisotropy compared to SiAuF3. Our analysis of optical properties unravels distinct characteristics. SiCuF3 boasts a higher refractive index at lower energies, indicating enhanced transparency in specific ranges, while SiAuF3 exhibits heightened reflectivity in select energy intervals. Further, both compounds exhibit remarkable absorption coefficients, showcasing their ability to absorb light at defined energy thresholds. The energy loss function (ELF) analysis uncovers differential absorption behavior, with SiAuF3 absorbing maximum energy at 6.9 eV and SiCuF3 at 7.2 eV. Our study not only enriches the fundamental understanding of SiAuF3 and SiCuF3 but also illuminates their potential in optoelectronic applications. These findings open doors to innovative technologies harnessing the distinctive qualities of these halide perovskite materials. As researchers seek materials that push the boundaries of optoelectronics and energy storage, SiAuF3 and SiCuF3 stand out as promising candidates, ready to shape the future of these fields.

Crystallization and defects regulation of efficient perovskite solar cells via surface induced secondary grain growth with formamidine iodine treatment

Trap–mediated non–radiative loss is a major efficiency and stability obstale for solution–processed perovskite solar cells (PSCs). To address this issue, defect passivation using organic molecules has been identified as an effective strategy due to the ionic nature of the perovskite lattice. Herein, Ostwald ripening by using formamidine iodine (FAI) is reported to inhibit the carrier trap induced recombination via promoting secondary grain growth at perovskite surface. Based on secondary grain growth with FAI treatment, the graded passivation was presented caused by FA+ and I- from FAI. Moreover, the findings from time resolved photoluminescence and space charge–limited current technology indicate enhancements in the crystal quality. Consequently, this approach yielded a remarkable power conversion efficiency (PCE) of 20.62% for the FAI modified MAPbI3 photovoltaics, with significantly improved open–circuit voltage ratio of 3.10%, short–circuit density ratio of 6.11%, fill factor ratio of 9.46% and PCE ratio of 19.06%. Moreover, the device show the excellent stability. This study introduces simple and reproducible procedures for fabricating PSCs, which can be readily extended to diverse optoelectronic device applications.

Dynamically Modulating the Dissymmetry Factor of Circularly Polarized Organic Ultralong Room‐Temperature Phosphorescence from Soft Helical Superstructures

AbstractAchieving circularly polarized organic ultralong room‐temperature phosphorescence (CP‐OURTP) with a high luminescent dissymmetry factor (glum) is crucial for diverse optoelectronic applications. In particular, dynamically controlling the dissymmetry factor of CP‐OURTP can profoundly advance these applications, but it is still unprecedented. This study introduces an effective strategy to achieve photoirradiation‐driven chirality regulation in a bilayered structure film, which consists of a layer of soft helical superstructure incorporated with a light‐driven molecular motor and a layer of room‐temperature phosphorescent (RTP) polymer. The prepared bilayered film exhibits CP‐OURTP with an emission lifetime of 805 ms and a glum value up to 1.38. Remarkably, the glum value of the resulting CP‐OURTP film can be reversibly controlled between 0.6 and 1.38 over 20 cycles by light irradiation, representing the first example of dynamically controlling the glum in CP‐OURTP.

Dynamically Modulating the Dissymmetry Factor of Circularly Polarized Organic Ultralong Room-Temperature Phosphorescence from Soft Helical Superstructures.

Achieving circularly polarized organic ultralong room-temperature phosphorescence (CP-OURTP) with a high luminescent dissymmetry factor (glum ) is crucial for diverse optoelectronic applications. In particular, dynamically controlling the dissymmetry factor of CP-OURTP can profoundly advance these applications, but it is still unprecedented. This study introduces an effective strategy to achieve photoirradiation-driven chirality regulation in a bilayered structure film, which consists of a layer of soft helical superstructure incorporated with a light-driven molecular motor and a layer of room-temperature phosphorescent (RTP) polymer. The prepared bilayered film exhibits CP-OURTP with an emission lifetime of 805 ms and a glum value up to 1.38. Remarkably, the glum value of the resulting CP-OURTP film can be reversibly controlled between 0.6 and 1.38 over 20 cycles by light irradiation, representing the first example of dynamically controlling the glum in CP-OURTP.

Ultrafast exciton trapping dynamics in oxygen-functionalized single-walled carbon nanotubes

Artificial zero-dimensional quantum defects within single-walled carbon nanotubes hold immense promise for diverse optoelectronic applications such as bioimaging, near-infrared light emission, nanolasing, and single-photon generation. This study delves into the temporal behavior of excitons within oxygen-functionalized single-walled carbon nanotubes, employing ultrafast transient absorption spectroscopy. Our investigation unveils the emergence of functionalization-induced excitonic states, distinguished by a long-lasting induced transmittance signal. Remarkably, even at low degree of functionalization, we observe a reduction in the lifetime of band-edge excitons. In contrast, the population dynamics of deep-band excitons exhibit resilience against low and moderate functionalization degrees, with a pronounced reduction manifesting only at high degrees of functionalization. Our findings align closely with a kinetic model that accounts for an additional relaxation channel prompted by functionalization. This empirical evidence provides a significant breakthrough, establishing that the formation of functionalization-induced excitonic states within oxygen-functionalized single-walled carbon nanotubes is a consequence of the diffusive trapping of free band edge excitons, while interaction of deep band excitons with oxygen defect sites rather yields in exciton recombination. These insights shed light on the intricate dynamics of excitons within single-walled carbon nanotube with artificially embedded quantum defects, advancing our understanding and potential applications in the realm of optoelectronics.

Perovskite Single Crystals with Self‐Cleaning Surface for Efficient Photovoltaics

AbstractMetal halide perovskite single crystals are promising for diverse optoelectronic applications. As a universal issue of solution‐grown perovskite single crystals, surface contamination causes adverse effect on material properties and device performance. Herein, learning from the self‐cleaning effect of lotus leaf, we address the surface contamination issue by introducing an amphiphilic long‐chain organic amine into the perovskite crystal growth solution. Self‐assembly of CTAC provides a hydrophobic crystal surface, inducing spontaneous removal of residual growth solution, which results in clean surface and better optoelectronic properties of perovskite single crystals. An impressive efficiency of 23.4 % is obtained, setting a new record for FAxMA1‐xPbI3 single‐crystal perovskite solar cells (PSCs). Moreover, our strategy also applies to perovskite single crystals with different morphology and composition, which may contribute to improvement of other single‐crystal perovskite optoelectronic devices.

Perovskite Single Crystals with Self-Cleaning Surface for Efficient Photovoltaics.

Metal halide perovskite single crystals are promising for diverse optoelectronic applications. As a universal issue of solution-grown perovskite single crystals, surface contamination causes adverse effect on material properties and device performance. Herein, learning from the self-cleaning effect of lotus leaf, we address the surface contamination issue by introducing an amphiphilic long-chain organic amine into the perovskite crystal growth solution. Self-assembly of CTAC provides a hydrophobic crystal surface, inducing spontaneous removal of residual growth solution, which results in clean surface and better optoelectronic properties of perovskite single crystals. An impressive efficiency of 23.4 % is obtained, setting a new record for FAx MA1-x PbI3 single-crystal perovskite solar cells (PSCs). Moreover, our strategy also applies to perovskite single crystals with different morphology and composition, which may contribute to improvement of other single-crystal perovskite optoelectronic devices.

Wafer-scale synthesis of two-dimensional ultrathin films.

Two-dimensional (2D) materials, consisting of atomically thin layered crystals, have attracted tremendous interest due to their outstanding intrinsic properties and diverse applications in electronics, optoelectronics, and catalysis. The large-scale growth of high-quality ultrathin 2D films and their utilization in the facile fabrication of devices, easily adoptable in industrial applications, have been extensively sought after during the last decade; however, it remains a challenge to achieve these goals. Herein, we introduce three key concepts: (i) the microwave assisted quick (∼1 min) synthesis of wafer-scale (6-inch) anisotropic conducting ultrathin (∼1 nm) amorphous carbon and 2D semiconducting metal chalcogenide atomically thin films, (ii) a polymer-assisted deposition process for the synthesis of wafer-scale (6-inch) 2D metal chalcogenide and pyrolyzed carbon thin films, and (iii) the surface diffusion and epitaxial self-planarization induced synthesis of wafer-scale (2-inch) single crystal 2D binary and large-grain 2D ferromagnetic ternary metal chalcogenide thin films. The proposed synthesis concepts can pave a new way for the manufacture of wafer-scale high quality 2D ultrathin films and their utilization in the facile fabrication of devices.

Non-innocent P-centers in nonbenzenoid polycyclic aromatic molecules with tunable structures and properties.

Implanting heteroatoms into polycyclic aromatic molecules (PAMs) offers a great opportunity to fine-tune their optoelectronic properties. Herein, we report a new type of nonbenzenoid PAM in which the sp2 C atoms are replaced by S and P in the azulene moiety. The synthesis harnessed modular P-chemistry and cyclization chemistry, which afforded the first example of P-azulene-based PAMs with isomeric PN- and PC-type structures. Photophysical and theoretical studies revealed that the P-environments have strong impacts on the structures and properties of the P-PAMs. Different from the electronic structure of azulene with strong π conjugation, the PC derivatives maintained effective σ*-π* hyperconjugation in the frontier molecular orbitals via the P-centers. In particular, the PC derivative with a P(iii)-center showed unexpected room-temperature phosphorescence in solution, which was attributed to the excited-state aromaticity induced structure change at the P-center. Decoration with various aryl groups further modified the photophysical and redox properties in another dimension. Furthermore, bis(triarylamine)-functionalized P-PAMs formed stable radical cations in which the P-environments strongly influenced the mixed-valence state and open-shell characters. As a proof of concept, bis(triarylamine)-functionalized P-PAMs were explored as the hole-transporting layers in perovskite solar cells, and a power conversion efficiency of 14% was achieved. As a new example of nonbenzenoid PAMs with intriguing optoelectronic properties, our P-PAMs are promising building blocks for diverse optoelectronic applications in the future.

Study on interface engineering and chemical bonding of the ReS2@ZnO heterointerface for efficient charge transfer and nonlinear optical conversion efficiency.

Rhenium sulfide (ReS2) has emerged as a promising two-dimensional material, demonstrating broad-spectrum visible absorption properties that make it highly relevant for diverse optoelectronic applications. Manipulating and optimizing the pathway of photogenerated carriers play a pivotal role in enhancing the efficiency of charge separation and transfer in novel semiconductor composites. This study focuses on the strategic construction of a semiconductor heterostructure by synthesizing ZnO on vacancy-containing ReS2 (VRe-ReS2) through chemical bonding processes. The ingeniously engineered built-in electric field within the heterostructure effectively suppresses the recombination of photogenerated electron-hole pairs. A direct and well-established interfacial connection between VRe-ReS2 and ZnO is achieved through a robust Zn-S bond. This distinctive bond configuration leads to enhanced nonlinear optical conversion efficiency, attributed to shortened carrier migration distances and accelerated charge transfer rates. Furthermore, theoretical calculations unveil the superior chemical interactions between Re vacancies and sulfide moieties, facilitating the formation of Zn-S bonds. The photoluminescence (PL) intensity is increased by the formation of VRe-ReS2 and ZnO heterostructure and the PL quantum yield of VRe-ReS2 is improved. The intricate impact of the Zn-S bond on the nonlinear absorption behavior of the VRe-ReS2@ZnO heterostructure is systematically investigated using femtosecond Z-scan techniques. The charge transfer from ZnO to ReS2 defect levels induces a transition from saturable absorption to reverse saturable absorption in the VRe-ReS2@ZnO heterostructure. Transient absorption measurements further confirm the presence of the Zn-S bond between the interfaces, as evidenced by the prolonged relaxation time (τ3) in the VRe-ReS2@ZnO heterostructure. This study offers valuable insights into the rational construction of heterojunctions through tailored interfacial bonding and surface/interface charge transfer pathways. These endeavors facilitate the modulation of electron transfer dynamics, ultimately yielding superior nonlinear optical conversion efficiency and effective charge regulation in optoelectronic functional materials.

Insight into the structural, optoelectronic, elastic and thermodynamic properties of new lead free double halides perovskites Cs2XCuF6 (X = Sc, Y): a first principle study

We conducted a thorough investigation of Cs2XCuF6 (X = Sc, Y) using a first-principles approach, exploring a wide range of material properties. We began by confirming the structural and thermodynamic stability of these compounds, employing analyses such as formation energy calculations, examination of the phonon band structure, and the utilization of the Birch-Murnaghan equation of state (EOS) curve. A noteworthy finding was the tunability of the band gaps in these double perovskite materials, achieved by substituting Sc with Y, resulting in a band gap range from 2.67 to 2.62 eV. Our analysis extended to the mechanical stability of these compounds, characterized by elastic constants and revealing mechanical anisotropy and ductility. Additionally, we explored the optical properties, highlighting their broad absorption band from the infrared (IR) to visible regions, which holds significant promise for diverse optoelectronic applications. To provide a comprehensive understanding of these materials, we delved into their thermodynamic properties, encompassing thermal expansion coefficients (κ), heat capacities, entropy (S), volume, and Debye Temperature (θ D). This investigation spanned a wide pressure range from 0 to 30 GPa and a temperature range from 0 to 1400 K, contributing to a holistic grasp of the fundamental characteristics of Cs2XCuF6 (X = Sc, Y).

Photoresponse of large-area atomically thin β-Ga2O3 and GaN materials via liquid metal print synthesized

This study uses liquid gallium metal to synthesize two-dimensional gallium oxide and gallium nitride ultra-thin layers. Addressing the challenges of conventional methods, this approach combines liquid metal properties with Polydimethylsiloxane (PDMS) transfer printing, resulting in large-area, highly clean, and low-residue amorphous Ga-based wide bandgap semiconductors. Transformation of amorphous Ga2O3 into crystallized β-Ga2O3 and GaN is achieved through annealing and ammoniation. Comprehensive characterizations confirm successful changes. Photodetector devices are fabricated and characterized, revealing Ga2O3 photosensitive nature with distinct performance metrics. GaN, while exhibiting lower photoresponse, displays rapid photocurrent recovery, making it promising for photodetector applications. This research offers a scalable method for two-dimensional gallium-group semiconductor synthesis, holding potential for diverse optoelectronic applications.

Surface defect passivation by copper incorporation for efficient perovskite solar cells

Defects play an important character in the degradation processes of hybrid halide perovskite, hindering their application for solar cells. Ion transport is facilitated by the ubiquitous organic cation and halide anion vacancy defects, which lead to perovskite disintegration at grain boundaries. In this article, a thorough investigation of the vacancy defect and defect density on perovskite is conducted by using VASP and SCAPS-1D. From SCAPS-1D, the PCE of the device increases from 17.82 % to 23.04 % when the defect state density drops from 10+15 to 10+14 cm-3. Therefore, reducing the defect density is very important to improve the performance of perovskite solar cells. Effective perovskite solar cells based on CH3NH3PbI3 incorporated copper ions passivation defects were carried out. Compare to pristine hybrid perovskite, Cu2+-doped hybrid perovskite have remarkably lower trap-state densities, greater film quality, and higher crystallinity. Especially, the maximum power conversion efficiency of up to 20.1 % was achieved with 0.5 % copper ion doping. After 500 h of not being enclosed in dry air, the devices still has 87 % of its original power conversion efficiency. Therefore, this work suggests that careful control the formation of Cu2+ in perovskite films is very important for diverse optoelectronic applications in the future.

Computational characterization of structural, optoelectronic and thermoelectric properties of some double half-Heusler alloys X2FeY′Sb2 (X: Hf, Zr ;Y′: Ni, Pd)

ABSTRACT A full-potential linear augmented plane wave (FP-LAPW) has been used to study the structural, electronic, and optical properties of double half-Heusler alloys X2FeY′Sb2 with X≡Zr, Hf and Y′≡Pd, Ni. Electronic band structures and densities of states calculations of the four studied double half-Heusler alloys indicate that they are semiconductors with an indirect gap. The optical spectra of dielectric constants, refractive indices, reflectivity, and light absorption are also discussed. In the energy range of 8–14 eV, the calculated optical properties and mainly the absorption spectrum show very high UV absorption. Additionally, DFT calculations were combined with Boltzmann transport theory to estimate the thermoelectric properties, such as the thermal and electrical conductivity, Seebeck coefficient, and figure of merit (ZT), versus the change of temperature and chemical potential. These alloys possess a suitable band gap for diverse optoelectronic applications, encompassing photovoltaics, UV sensors, and solar cells.

Composition-Property Relations for GAx FAy MA1- x - y PbI3 Perovskites.

Halide perovskites are materials for diverse optoelectronic applications owing to a combination of factors, including their compositional flexibility. A major source of this diversity of compositions comes from the use of mixed organic cations in the A-site of such compounds to form solid solutions. Many organic cations are possible for this purpose. Although significant progress is made over years of intensive research, the determination of systematic relationships between the compositions and properties of halide perovskites is not exploited accordingly. Using the MAPbI3 prototype, a wide range of compositions substituted by formamidinium (FA+ ) and guanidinium (GA+ ) cations are studied. From a detailed collection of experimental data and results reported in the literature, heat maps correlating the composition of GAx FAy MA1- x - y PbI3 solid solutions with phase transition temperatures, dielectric permittivity, and activation energies are constructed. Considering the characteristics of organic cations, namely their sizes, dipole moments, and the number of N─H bonds, it is possible to interpret the heat maps as consequences of these characteristics. This work brings a systematization of how obtaining specific properties of halide perovskites might be possible by customizing the characteristics of the A-site organic cations.

Fast optoelectronic gas sensing with p-type V2O5/WS2/Si heterojunction thin film

The efficiency of ultraviolet (UV) illumination in gas adsorption/desorption is remarkable due to its capacity to activate and energize CO2 molecules, rendering them more reactive and prone to surface interactions. A heterojunction device for room-temperature optoelectronic gas sensing has been fabricated. This was achieved through the deposition of an orthorhombic vanadium pentoxide (V2O5) thin film onto a wafer scale 2D p-type tungsten disulfide (WS2)/silicon (Si). The incorporation of the V2O5 layer brings about alterations in WS2's electronic properties, resulting in increased energy states for photo-generated carriers and a promising approach to enhance the intensity of exciton and trion peaks. Specifically, the WS2 film exhibits a carrier concentration of 3.67 × 1018 cm−3, while incorporating the V2O5 layer significantly raises this concentration to 1.20 × 1020 cm−3. The experiments reveal a rapid response time of 0.4 s and a recovery time of 0.2 s, respectively, demonstrating the swift desorption capability of the device in a CO2 environment. Remarkably, this device exhibits high optoelectronic performances, boasting a detectivity of 1.22 × 1013 Jones and a responsivity of 177.21 A/W. These findings have the potential to advance the development of improved gas-sensing devices, offering heightened sensitivity and selectivity in diverse optoelectronic applications.

Toward first-principles approaches for mechanistic study of self-trapped exciton luminescence

In recent years, broadband photo-luminescence phenomena arising from self-trapped exciton (STE) in metal halides, including perovskites and various low-dimensional derivatives and variants, have attracted increasing attention for their potential diverse optoelectronic applications like lighting, display, radiation detection, and sensing. Despite great success in experimental discovery of many efficient STE emitters, the current understanding of the STE emission mechanism in metal halides is still immature, and often controversial, which calls for help urgently from predictive first-principles theoretical calculation. Although density-functional theory (DFT) based calculations are routinely used to provide electronic band structure of materials and have contributed greatly to qualitative analysis of luminescence mechanism, more in-depth and quantitative information is highly needed to provide guidelines for rational design of new luminescent materials with desirable features. However, due to the complicated nature of STE emission, involving in particular electron–phonon coupling in both ground and excited states, the usage of DFT is no longer a routine job as for ground state properties. While more sophisticated methods formulated in the framework of many-body perturbation theory like GW-Bethe–Salpeter equation are available and provide theoretically rigorous and accurate description of electronic transitions in extended systems, their application to real STE systems is still severely limited due to highly demanding computational cost. In practice, approximated DFT methods are employed, which have their own strengths and limitations. In this review, we focus on the theoretical approaches that have been heavily used in interpreting STE luminescence mechanism, with a particular emphasis on theoretical methods for exciton self-trapping structural optimization. It is hoped that this review, by summarizing the current status and limitations of theoretical research in the STE emission, will motivate more methodological development efforts in this important field, and push forward the frontiers of excited state electronic structure theory of materials in general.

Negligible Bowing Effect of Bandgap and Lattice Constant in a Variety of Compositions using Large Tilt Distortion in a Cesium–Lead Mixed‐Halide System

AbstractHalide perovskites have broad bandgap tunability, making them suitable for diverse applications in optoelectronics and photovoltaics. The optical bandgap of halide perovskites varies almost linearly with the halide ionic size, and therefore, it can be controlled through compositional engineering. However, the mechanism underlying this low‐bandgap variation is not yet fully understood. Thus, this study comprehensively investigates the bandgap bowing of cesium–lead mixed‐halide perovskites using compositional engineering and demonstrates that bandgap bowing is extremely small in a variety of compositions including Cl, Br, and I. Subsequently, through density functional theory calculations, it is suggested that the antibonding character of the valence band maximum, tilt distortion of halide ions, and entropy effect leading to equal participation of various halide ions around Pb are collectively responsible for the small bandgap bowing.

Fluorinated Organic A‐Cation Enabling High‐Performance Hysteresis‐Free 2D/3D Hybrid Tin Perovskite Transistors

Abstract2D tin‐based perovskites have gained considerable attention for use in diverse optoelectronic applications, such as solar cells, lasers, and thin‐film transistors (TFTs), owing to their good stability and optoelectronic properties. However, their intrinsic charge‐transport properties are limited, and the insulating bulky organic ligands hinder the achievement of high‐mobility electronics. Blending 3D counterparts into 2D perovskites to form 2D/3D hybrid structures is a synergistic approach that combine the high mobility and stability of 3D and 2D perovskites, respectively. In this study, reliable p‐channel 2D/3D tin‐based hybrid perovskite TFTs comprising 3D formamidinium tin iodide (FASnI3) and 2D fluorinated 4‐fluoro‐phenethylammonium tin iodide ((4‐FPEA)2SnI4) are reported. The optimized FPEA‐incorporated TFTs show a high hole mobility of 12 cm2 V−1 s−1, an on/off current ratio of over 108, and a subthreshold swing of 0.09 V dec−1 with negligible hysteresis. This excellent p‐type characteristic is compatible with n‐type metal‐oxide TFT for constructing complementary electronics. Two procedures of antisolvent engineering and device patterning are further proposed to address the key concern of low‐performance reproducibility of perovskite TFTs. This study provides an alternative A‐cation engineering method for achieving high‐performance and reliable tin‐halide perovskite electronics.