The film thickness dependent thermal stability of Al2O3:Ag thin films as high-temperature solar selective absorbers

The monolayer Al2O3:Ag thin films were prepared by magnetron sputtering. The microstructure and optical properties of thin film after annealing at 700 degrees C in air were characterized by transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and spectrophotometer. It revealed that the particle shape, size, and distribution across the film were greatly changed before and after annealing. The surface plasmon resonance absorption and thermal stability of the film were found to be strongly dependent on the film thickness, which was believed to be associated with the evolution process of particle diffusion, agglomeration, and evaporation during annealing at high temperature. When the film thickness was smaller than 90 nm, the film SPR absorption can be attenuated until extinct with increasing annealing time due to the evaporation of Ag particles. While the film thickness was larger than 120 nm, the absorption can keep constant even after annealing for 64 h due to the agglomeration of Ag particles. On the base of film thickness results, the multilayer Al2O3:Ag solar selective thin films were prepared and the thermal stability test illustrated that the solar selectivity of multilayer films with absorbing layer thickness larger than 120 nm did not degrade after annealing at 500 degrees C for 70 h in air. It can be concluded that film thickness is an important factor to control the thermal stability of Al2O3:Ag thin films as high-temperature solar selective absorbers.</p

High Shunt Resistance SnO2-PbO Electron Transport Layer for Perovskite Solar Cells Used in Low Lighting Applications

Hybrid perovskites are promising materials for new sustainable photovoltaic applications to operate under low lighting conditions, such as the reuse of residual photons that are wasted during indoor lighting. The requirements for a perovskite solar cell (PSC) to offer maximum power conversion efficiency (PCE) under low illumination conditions are not totally clear in the literature. In this work, the PCE of the commonly used SnO2 electron transport layer (ETL) is improved by a facile method, doping the precursor nanoparticles with small concentrations of a Pb source. Under low illumination conditions (i.e., 0.1 mW cm−2) the PCE is enhanced from 18.8% to 34.2%. From a complete analysis of the ETLs and devices using several structural and electrical techniques it is observed that the parameter that improves the most is the shunt resistance of the device which avoids the parallel leakage of the photogenerated current. The present work clearly shows that the shunt resistance is a very important parameter that needs to be optimized in PSCs for low illumination conditions.Funding for open access charge: CRUE-Universitat Jaume IThis work was supported by the Project on Collaborative Innovation and Environmental Construction Platform of Guangdong Province (No. 2018A050506067). The authors also thank the financial support from the Key Laboratory of Renewable Energy, Chinese Academy of Sciences (No. y807j71001), Guangdong Provincial Key Laboratory of New and Renewable Energy Research and Development (Grant No. Y909kp1001), and the Key Project on Synergy Collaborative Innovation of Guangzhou City (No. 201704030069). University Jaume I is also acknowledged for financial support (No. UJI-B2020-49)

Metal Halide Perovskites Functionalized by Patterning Technologies

Metal halide perovskites (MHPs), as emerging stars, are greatly attracted due to their superior optical and optoelectrical properties. The design and construction of patterned materials have been considered as a powerful tool to improve the performance of optical and optoelectronic devices. Therefore, the marriage of MHPs and patterning technologies is expected to boost the development of perovskite-based applications with novel functions and optimized properties. Moreover, with the merits of patterning technologies, integrated and small-sized perovskite-based optoelectronic devices with compactness are foreseen. In this review, recent progress in this field is summarized, including template-assisted and template-free patterning technologies that can endow MHPs with high crystallinity, long-term stability, and special structures. Besides, the advantages and mechanisms of patterned MHPs toward high-performance applications are discussed

Ellipsometric studies of optical properties of Er-doped ZnO thin films synthesized by sol-gel method

We have reported a low-cost and fast formation of highly efficient Er centers in ZnO thin films. As a high sensitivity tool for the detection of trace of Er dopant in ZnO film, spectroscopic ellipsometry is employed to disclose the systematic interrelationship of the crystallinity, dielectric function and optical band structure. Pure ZnO thin film shows very sharp band structure. The films with 0.05 at.% Er dopant, annealed at 600 degrees C and 800 degrees C, exhibit the similar tendency where the dopant level appears at the band tail. The band structure of the films with 0.05 at.% Er dopant, annealed at 400 degrees C, is very close to that of pure ZnO. While the samples annealed at 1000 degrees C are on the verge of amorphousness, and the flat curve of photon energy dependent epsilon(i)(E) is observed. The strain effect caused by the formation of ErO6 pseudo-octahedron structure greatly affects the value of dielectric constants. Therefore, SE analyses reveal significant effect of Er doping and annealing temperatures on the modification of optical band structure, dielectric property and optically active center in ZnO films. (C) 2013 Elsevier B.V. All rights reserved

Influence of Annealing on the Structure and 1.54 mu m Photoluminescence of Er-Doped ZnO Thin Films Prepared by Sol-Gel Method

We have investigated the effects of Er concentration, post-annealing time and temperature through a sol-gel preparation method on the structure and 1.54-mu m-related photoluminescence (PL) of ZnO:Er thin films. The results illustrated that the 1.54 mu m emission was greatly influenced by the local structure of Er-O complex and ZnO host. The active oxygen movement during annealing process resulted in the formation of optical active center of Er ions, which probably attributed to the formation of a similar pseudo-octahedron with C-4v structure around Er. The preferential orientation of ZnO host had more effect on the 1.54 mu m PL intensity than the crystallinity of ZnO host. Therefore, the optimum annealing condition was about 800 degrees C/2 h and the appropriate concentration was about 0.05 at % Er. A low-cost and fast formation of highly efficient Er centers in ZnO host for strong luminescence at near-infared region should be benefit for both fundamental research and also applications of light-emitting devices. (C) 2011 The Japan Society of Applied Physic

Microstructure and Optical Properties of Sm3+ Doped TiO2 Thin Films by Oblique Angle Deposition

TiO2: 2%Sm3+ thin films were prepared by oblique angle deposition. X-ray diffraction (XRD), scanning electron microscope (SEM), UV-Vis-NIR spectrophotometer, fluorescence spectrophotometer was employed to characterize the structure and optical properties of TiO2: 2%Sm3+ thin films. The results indicated that these thin films were with anisotropic columnar structure before and after calcination. The optical anisotropy measured by transmission difference (Tp-Ts) at 500nm was increasing from 8% to 33% with calcination. Under ultraviolet excitation (lambda(ex) = 330nm) and commercial 365nm UV lamp excitation, these TiO2: Sm3+ thin films show intense (4)G(5/2)-> H-6(5/2), (7/2), (9/2) emissions of Sm3+. The polarized photoluminescence was anticipated in the anisotropic thin films

A facile method to prepare ultra-wideband anti-reflective borosilicate glass with subwavelength structure surface

Anti-reflective (AR) films have been widely investigated due to their various applications in optoelectronic devices. Among all the investigation, the manufacturing method is the most popular research field which directly determines the performance of anti-reflective films. Herein, Na2HPO4 and AlCl3 mixed neutral solution were used to etch the surface of K9 glass matrix to obtain the AR structure. The morphology of SEM images indicated that subwavelength structure (SWS) was formed on the glass surface via precisely controlling the solution concentration, treatment time and temperature. Owing to the porous structure, the refractive index mutation of the interface between air and glassss can be effectively weakened. Therefore, the integral transmittance, covering the whole visible light (VIS) to near-infrared (NIR) wavelength (300-2500 nm), of glass matrix was increased remarkably to 95.77%, much higher than 87.72% of blank glass, achieving the effect of ultra-wideband anti-reflection. Particularly, the transmittance at 520 nm and 1990 nm can even reach to 99.14% and 97.86%, respectively. According to the composite analysis and reaction process, Al3+ ions act as both the regulator of the solution pH and part of the new-formed glass skeleton, resulting in the more uniform and regular SWS on the glass surface. Moreover, in virtue of -OH in silanol (Si-OH) on the expanded glass surface attracting more H2O molecules or additional silylation modification on glass surface repulsing H2O molecules, the surface characteristics of AR glass with SWS films can be easily turned between hydrophilic and hydrophobic in order to meet the requirements of various application environments. These ultra-wideband AR glasses with controllable hydrophilic and hydrophobic properties are expected to be applied in many optoelectronic fields

Anisotropic Laser-Induced Damage Threshold and Residual Stress of TiO2 Sculptured Thin Films

The residual stress and laser-induced damage threshold (LIDT) of TiO2 sculptured thin films prepared by glancing angle electron beam evaporation were studied. UV-Vis-NIR spectra and optical interferometer were employed to characterize the optical and mechanical properties, respectively. Optical microscopy and Raman spectra were used to observe damage morphology and analyze damage microstructure, respectively. It was found that the residual stress changed from compressive into tensile with increasing deposition angle. The LIDT was anisotropic with p- and s-polarization light, which was due to the anisotropic nanostructure and optical properties. Simultaneously, an optimum deposition angle for the maximum threshold of TiO2 film was about 60 degrees. The mechanism of laser-induced damage was thermal in nature. The process of thermal damage with crystallization is proved by Raman spectra

Structure and optical properties of carbon-TiO2 composite thin films by sol-gel method as solar selective absorbers

C-TiO2 thin films as low cost solar selective absorbers were prepared by sol-gel method and post-annealing. Differential scanning calorimetry (DSC), Raman spectroscopy, X-ray diffraction (XRD), High-resolution transmission electron microscope (HR-TEM), Field emission scanning electron microscopy (FE-SEM), UV-Vis-NIR spectrophotometer are employed to characterize the structure and optical properties. The results illustrated that C-TiO2 composite thin films can be obtained after spinning and post-annealing. The solar absorptance (alpha) and thermal emissivity (epsilon) vary with carbon content and annealing conditions. The optimal annealing condition is 500 degrees C/2 h and the optimal carbon content is about 0.6 with alpha = 0.87 and epsilon = 0.13. C-TiO2 composite thin films own good thermal stability at 100 degrees C, which proves that it can be a good candidate as low-temperature solar selective absorbers

Economical Salt-Resistant Superhydrophobic Photothermal Membrane for Highly Efficient and Stable Solar Desalination

Recently, solar-driven interfacial water evaporation has shown great potential in desalination. In a practical application, the inevitable pollution and accumulation of salt that make the evaporation efficient cannot be maintained for a long time. Herein, we report a flexible and economical superhydrophobic photo-thermal membrane composed of polyvinylpyrrolidone (PVP) and carbon nanotubes (CNTs) with a 1H,1H,2H,2H-perfluorodecyl-triethoxysilane modification, with a piece of expanded polystyrene used for support and thermal insulation. The prepared floating evaporation device showed a high energy efficiency of 91.1% and an evaporation rate of 1.41 kg m(-2)h(-1) under one solar irradiation, and neither salt accumulation nor a significant decrease in the evaporation rate of the device was observed after continuous operation for either 40 h or 18 evaporation cycles. In addition, the self-cleaning performance of the membrane enabled its surface to maintain high absorbance for a long time. With the stable and efficient evaporation performance of this device, it provided guidance for the application of efficient and long-term stable solar desalination