Novel supramolecular luminescent metallogels containing Tb(iii) and Eu(iii) ions with benzene-1,3,5-tricarboxylic acid gelator: advancing semiconductor applications in microelectronic devices.

A novel strategy was employed to create supramolecular metallogels incorporating Tb(iii) and Eu(iii) ions using benzene-1,3,5-tricarboxylic acid (TA) as a gelator in N,N-dimethylformamide (DMF). Rheological analysis demonstrated their mechanical robustness under varying stress levels and angular frequencies. FESEM imaging revealed a flake-like hierarchical network for Tb-TA and a rod-shaped architecture for Eu-TA. EDX analysis confirmed essential chemical constituents within the metallogels. FT-IR, PXRD, Raman spectroscopy, and thermogravimetric analysis assessed their gelation process and material properties, showing semiconducting characteristics, validated by optical band-gap measurements. Metal-semiconductor junction-based devices integrating Al metal with Tb(iii)- and Eu(iii)-metallogels exhibited non-linear charge transport akin to a Schottky diode, indicating potential for advanced electronic device development. Direct utilization of benzene-1,3,5-tricarboxylic acid and Tb(iii)/Eu(iii) sources underscores their suitability as semiconducting materials for device fabrication. This study explores the versatile applications of Tb-TA and Eu-TA metallogels, offering insights for material science researchers.

Super-hydrophilic LaCoO3/g-C3N4 nanocomposite coated beauty sponge for solar-driven seawater desalination with simultaneous volatile organic compound removal.

Interfacial solar steam generation (ISSG) is emerging as a promising, environment-friendly solution for fulfilling freshwater and energy demands. However, a critical challenge for ISSG lies in the presence of harmful volatile organic compounds (VOCs) in the feedwater which are co-evaporated with water, leading to more enriched concentration in condensed water. Herein, lanthanum cobaltate-graphitic carbon nitride (LaCoO3/g-C3N4, LCO/g-CN) nanocomposite decorated beauty sponge (LCO/g-CN@BS) is proposed as an efficient photothermal/photocatalytic material for solar-driven seawater desalination and simultaneous VOC degradation. The hydrophobic surface of the beauty sponge after LCO/g-CN coating becomes super-hydrophilic, ensuring sufficient water supply and our LCO/g-CN@BS delivers an evaporation rate of 1.94 kg m-2 h-1 under 1 sun irradiation. This LCO/g-CN@BS shows excellent seawater desalination capacity with a self-cleaning ability when employed for saltwater purification for a salt (NaCl) concentration as high as 15 wt%. Moreover, fast photocarrier transfer between LCO and g-CN leads to enhanced photocatalytic degradation of over 90% of phenol simultaneously, which is about 60% for only an LCO-based beauty sponge. This work presents a promising approach to combining novel nanocomposites with microporous structures for efficient solar desalination, offering simultaneous VOC degradation.

Microfluidic Salinity Gradient-Induced All-Day Electricity Production in Solar Steam Generation.

Synergistic generation of freshwater and electricity using solar light would be an ideal solution for global freshwater challenges and energy demands. Recently, interface solar steam generation has been considered one of the promising cost-effective alternatives for freshwater generation. Here, we have systematically maintained the salinity gradient within two-legged paper-based microfluidic channels to transport wastewater from the reservoir to the evaporator surface and generate electricity all-day-long. Flowing seawater (3.5 wt % NaCl) on one leg and tap water on the other of the water-conducting channels connected to a conical evaporator, we achieved an average open-circuit voltage (VOC) of 150 mV and a short-circuit current of 6.5 µA across each channel along with a water evaporation efficiency of 88%. As the VOC depends only on the ion concentration gradient within the channel in the direction perpendicular to the water flow, the electricity generation persists throughout the day and can be tuned by varying the salinity. Increasing the salt concentration of the seawater to 20 wt %, the VOC increased to 250 mV in a single channel. In an evaporator connected with four such channels, we achieved a maximum output power density of 9.9 mW m-2 in a series combination without sacrificing the evaporation rate. Furthermore, removing agglomerated salt from the evaporator surface, we harvested salt at a rate of 0.33 kg m-2 h-1. Therefore, our approach provides an alternative way of freshwater generation, salt harvesting, and all-day-long electricity production simultaneously.

Narrow-Bandgap LaMO3 (M = Ni, Co) nanomaterials for efficient interfacial solar steam generation.

Photothermal water evaporation provides a pathway towards a promising solution to global freshwater scarcity. Synergistic integration of functions in a material in diverse directions is a key strategy for designing multifunctional materials. Lanthanum-based perovskite complex oxides LaMO3 (M = Ni and Co) have narrow band gaps with a high absorption coefficient. These functionalities have not been appropriately explored for photothermal energy conversion. Here, we synthesized nanostructured metallic LaNiO3 and semiconducting LaCoO3 and used them to design interfacial solar steam generators. Effective light absorption capability over the entire solar spectrum of these materials leads to a photothermal efficiency of the order of 83% for both materials. Using a cone-shaped 3D interfacial steam generator with a LaNiO3 absorber, we achieved an evaporation rate of 2.3 kg m-2 h-1, corresponding to solar vapor generation efficiency of over 95%. To the best of our knowledge, this evaporation rate is higher than any oxide-based interfacial solar steam generator reported so far. Furthermore, we have also shown an effective way of using such evaporators for long-term seawater desalination.

Effects of High Temperature and Thermal Cycling on the Performance of Perovskite Solar Cells: Acceleration of Charge Recombination and Deterioration of Charge Extraction.

In this work, we investigated the effects of high operating temperature and thermal cycling on the photovoltaic (PV) performance of perovskite solar cells (PSCs) with a typical mesostructured (m)-TiO2-CH3NH3PbI3-xClx-spiro-OMeTAD architecture. After temperature-dependent grazing-incidence wide-angle X-ray scattering, in situ X-ray diffraction, and optical absorption experiments were carried out, the thermal durability of PSCs was tested by subjecting the devices to repetitive heating to 70 °C and cooling to room temperature (20 °C). An unexpected regenerative effect was observed after the first thermal cycle; the average power conversion efficiency (PCE) increased by approximately 10% in reference to the as-prepared device. This increase of PCE was attributed to the heating-induced improvement of the crystallinity and p doping in the hole transporter, spiro-OMeTAD, which promotes the efficient extraction of photogenerated carriers. However, further thermal cycles produced a detrimental effect on the PV performance of PSCs, with the short-circuit current and fill factor degrading faster than the open-circuit voltage. Similarly, the PV performance of PSCs degraded at high operation temperatures; both the short-circuit current and open-circuit voltage decreased with increasing temperature, but the temperature-dependent trend of the fill factor was the opposite. Our impedance spectroscopy analysis revealed a monotonous increase of the charge-transfer resistance and a concurrent decrease of the charge-recombination resistance with increasing temperature, indicating a high recombination of charge carriers. Our results revealed that both thermal cycling and high temperatures produce irreversible detrimental effects on the PSC performance because of the deteriorated interfacial photocarrier extraction. The present findings suggest that the development of robust charge transporters and proper interface engineering are critical for the deployment of perovskite PVs in harsh thermal environments.

Sb2S3/Spiro-OMeTAD Inorganic-Organic Hybrid p-n Junction Diode for High Performance Self-Powered Photodetector.

Organic-inorganic hybrid diodes are very promising for solution processing, low cost, high performance optoelectronic devices. Here, we report a high quality p-n heterojunction diode composed of n-type inorganic Sb2S3 and p-type organic 2,2',7,7'-tetrakis-(N,N-di-p-methoxyphenylamine)-9,9'-spirobifluorene (spiro-OMeTAD) with a rectification ratio of ∼102 at an applied bias of 1 V. On illumination with visible light (470 nm, 1.82 mW/cm2), the current value in our device becomes 8 × 102 times that of its dark value even at a zero bias condition. The estimated responsivity value at zero bias is 0.087 A/W which is so far the highest reported for any organic-inorganic hybrid photodiode, to the best of our knowledge. It also exhibits a fast photoresponse time of <25 ms (instrumental limit). More importantly, our device can also detect visible light with power density as low as 8 µW/cm2 with a photocurrent density of 1.2 µA/cm2 and a photocurrent to dark current ratio of more than 8. We also demonstrate that the values of responsivity, short circuit current, and open circuit voltage of the photodetector can be improved significantly using a thin layer of TiO2 hole-blocking layer. These findings suggest Sb2S3/spiro-OMeTAD heterojuncton as a promising candidate for efficient self-powered low visible light photodetector.

Real-Space Mapping of Surface Trap States in CIGSe Nanocrystals Using 4D Electron Microscopy.

Surface trap states in copper indium gallium selenide semiconductor nanocrystals (NCs), which serve as undesirable channels for nonradiative carrier recombination, remain a great challenge impeding the development of solar and optoelectronics devices based on these NCs. In order to design efficient passivation techniques to minimize these trap states, a precise knowledge about the charge carrier dynamics on the NCs surface is essential. However, selective mapping of surface traps requires capabilities beyond the reach of conventional laser spectroscopy and static electron microscopy; it can only be accessed by using a one-of-a-kind, second-generation four-dimensional scanning ultrafast electron microscope (4D S-UEM) with subpicosecond temporal and nanometer spatial resolutions. Here, we precisely map the collective surface charge carrier dynamics of copper indium gallium selenide NCs as a function of the surface trap states before and after surface passivation in real space and time using S-UEM. The time-resolved snapshots clearly demonstrate that the density of the trap states is significantly reduced after zinc sulfide (ZnS) shelling. Furthermore, the removal of trap states and elongation of carrier lifetime are confirmed by the increased photocurrent of the self-biased photodetector fabricated using the shelled NCs.

Heterostructured WS2 /CH3 NH3 PbI3 Photoconductors with Suppressed Dark Current and Enhanced Photodetectivity.

Heterostructured photoconductors based on hybrid perovskites and 2D transition-metal dichalcogenides are fabricated and characterized. Due to the superior properties of CH3 NH3 PbI3 and WS2 , as well as the efficient interfacial charge transfer, such photoconductors show high performance with on/off ratio of ≈10(5) and responsivity of ≈17 A W(-1) . Furthermore, the response times of the heterostructured photoconductors are four orders of magnitude faster compared to the counterpart of a perovskite single layer.

Solution-Grown Monocrystalline Hybrid Perovskite Films for Hole-Transporter-Free Solar Cells.

High-quality perovskite monocrystalline films are successfully grown through cavitation-triggered asymmetric crystallization. These films enable a simple cell structure, ITO/CH3 NH3 PbBr3 /Au, with near 100% internal quantum efficiency, promising power conversion efficiencies (PCEs) >5%, and superior stability for prototype cells. Furthermore, the monocrystalline devices using a hole-transporter-free structure yield PCEs ≈6.5%, the highest among other similar-structured CH3 NH3 PbBr3 solar cells to date.

ZnO Nanorods on a LaAlO3 -SrTiO3 Interface: Hybrid 1D-2D Diodes with Engineered Electronic Properties.

Integrating nanomaterials with different dimensionalities and properties is a versatile approach toward realizing new functionalities in advanced devices. Here, a novel diode-type heterostructure is reported consisting of 1D semiconducting ZnO nanorods and 2D metallic LaAlO3-SrTiO3 interface. Tunable insulator-to-metal transitions, absent in the individual components, are observed as a result of the competing temperature-dependent conduction mechanisms. Detailed transport analysis reveals direct tunneling at low bias, Fowler-Nordheim tunneling at high forward bias, and Zener breakdown at high reverse bias. Our results highlight the rich electronic properties of such artificial diodes with hybrid dimensionalities, and the design principle may be generalized to other nanomaterials.

Fast Crystallization and Improved Stability of Perovskite Solar Cells with Zn2SnO4 Electron Transporting Layer: Interface Matters.

Here we report that mesoporous ternary oxide Zn2SnO4 can significantly promotes the crystallization of hybrid perovskite layers and serves as an efficient electron transporting material in perovskite solar cells. Such devices exhibit an energy conversion efficiency of 13.34%, which is even higher than that achieved with the commonly used TiO2 in the similar experimental conditions (9.1%). Simple one-step spin coating of CH3NH3PbI3-xClx on Zn2SnO4 is found to lead to rapidly crystallized bilayer perovskite structure without any solvent engineering. Furthermore, ultrafast transient absorption measurement reveals efficient charge transfer at the Zn2SnO4/perovskite interface. Most importantly, solar cells with Zn2SnO4 as the electron-transporting material exhibit negligible electrical hysteresis and exceptionally high stability without encapsulation for over one month. Besides underscoring Zn2SnO4 as a highly promising electron transporting material for perovskite solar cells, our results demonstrate the significant role of interfaces on improving the perovskite crystallization and photovoltaic performance.

Temperature-dependent excitonic photoluminescence of hybrid organometal halide perovskite films.

Organometal halide perovskites have recently attracted tremendous attention due to their potential for photovoltaic applications, and they are also considered as promising materials in light emitting and lasing devices. In this work, we investigated in detail the cryogenic steady state photoluminescence properties of a prototypical hybrid perovskite CH3NH3PbI3-xClx. The evolution of the characteristics of two excitonic peaks coincides with the structural phase transition around 160 K. Our results further revealed an exciton binding energy of 62.3 ± 8.9 meV and an optical phonon energy of 25.3 ± 5.2 meV, along with an abnormal blue-shift of the band gap in the high-temperature tetragonal phase.

Pd-nanoparticle-decorated ZnO nanowires: ultraviolet photosensitivity and photoluminescence properties.

ZnO nanowires (NWs) have been decorated with Pd nanoparticles of sizes less than 10 nm (Pd-ZnO NWs) via a chemical solution route. The microstructural characterizations have been done using field emission scanning electron and high-resolution transmission electron microscopes. The effects of attaching Pd nanoparticles to the walls of ZnO NWs have been investigated by studying the ultraviolet (UV) photosensitivity and photoluminescence (PL) properties. The surface-modified NWs show a UV photosensitivity more than double and a response seven times faster compared to the bare NWs. The photocarrier relaxation under the steady UV illumination condition is quite different in Pd-ZnO NWs. The higher and faster photosensitivity has been explained on the basis of photocarrier transfer from the conduction band of ZnO to the Fermi level of Pd and subsequent electron trapping by the adsorbed O(2) molecules on the NWs' surface, which have been presented through a proposed model. The PL spectrum of Pd-ZnO NWs shows that the intensities of the band-edge and defect-related emissions decrease and increase, respectively, due to Pd anchoring, the effect being pronounced as the density of Pd nanoparticles increases.

Ordered dispersion of ZnO quantum dots in SiO2 matrix and its strong emission properties.

ZnO nanoparticles in the form of quantum dots (QDs) have been dispersed in SiO(2) matrix using StÖber method to form ZnO QDs-SiO(2) nanocomposites. Addition of tetraethyl orthosilicate (TEOS) to an ethanolic solution of ZnO nanoparticles produces random dispersion. On the other hand, addition of ZnO nanoparticles to an already hydrolyzed ethanolic TEOS solution results in a chain-like ordered dispersion. The photoluminescence spectra of the as-grown nanocomposites show strong emission in the ultraviolet region. When annealed at higher temperature, depending on the sample type, these show strong red or white emission. Interestingly, when the excitation is removed, the orderly dispersed ZnO QDs-SiO(2) composite shows a very bright blue fluorescence visible by naked eyes for few seconds indicating their promise for display applications. The emission property has been explained in the light of structure-property relationship.

Photoluminescence and photoconductivity of ZnS-coated ZnO nanowires.

ZnO nanowires (NWs) with a ZnS coating are synthesized in order to modify the surface without changing the diameter of the NWs. They have the wurtzite ZnO at the core and a cubic ZnS at the outer layer. The NWs show a sharp ultraviolet and a broad visible emission of the photoluminescence spectra. Surface modification has led to a change in the position of the maxima of the visible emission in ZnO-ZnS NWs. The photocarrier relaxation under steady UV illumination occurs in ZnO NW arrays but is absent in ZnO-ZnS NW arrays. The dark current value for both type of NWs are similar, whereas the photocurrent value is much higher in the surface-modified NWs. Higher photocurrent value indicates a transport of the photogenerated carriers from the ZnS layer to ZnO during UV illumination. The carrier transport mechanism is proposed through a model.

Effect of surface capping with poly(vinyl alcohol) on the photocarrier relaxation of ZnO nanowires.

The effect of surface capping with poly(vinyl alcohol) (PVA) on the photocarrier relaxation of the aqueous chemically grown ZnO nanowires (NWs) has been investigated. The decay in the photocurrent during steady ultraviolet illumination due to the photocarrier relaxation has been reduced in the capped NWs, as evidenced from a decrease in the photocurrent only by 12% of its maximum value under steady illumination for 15 min and a decrease in the photocurrent by 49% of its maximum value during the same interval of time in the as-grown NWs. The surface modification is confirmed from the FESEM, HRTEM, and FTIR results. The photoluminescence spectrum shows an enhanced ultraviolet emission and a reduced defect-related emission in the capped ZnO NWs compared to bare ZnO.

Encapsulation of 2-3-nm-sized ZnO quantum dots in a SiO2 matrix and observation of negative photoconductivity.

Quantum dots (QDs) of ZnO of 2-4 nm size have been encapsulated within a SiO(2) matrix using aqueous chemically grown ZnO nanoparticles in a precursor of tetraethyl orthosilicate. The microstructure shows almost a uniform embedment of the QDs in the SiO(2) matrix, resulting in a ZnO QDs-SiO(2) composite structure. The photocurrent transients of the composite show an instant fall in the current followed by an exponential decay under ultraviolet (UV) illumination, causing negative photoconductivity (NPC), in contrast to the positive photoconductivity in only ZnO nanoparticles. The interface defect states due to the presence of the SiO(2) network around ZnO act as charge trap centers for the photoexcited electrons and are responsible for the NPC. The presence of interface-trapped charges under UV illumination has been further confirmed from capacitance-voltage measurements.