Data_Sheet_1_High-Performance Perovskite Solar Cells Based on Low-Temperature Processed Electron Extraction Layer.PDF

Organic-inorganic perovskite solar cells (PSCs) is considered one of the most promising energy harvesting technologies due to its high power conversion efficiency (PCE). The T. Miyasaka group first reported the methylammonium lead halide (CH3NH3PbX3) as a light absorber of dye-sensitized solar cells with a PCE of 3.8% in 2009. Over the past decade, many research groups have been dedicated to constructing high-performance PSCs and have obtained fantastic progress. Before commercialization, many issues have to be overcome. To extend the application of PSCs, flexible PSCs are seen as the preferred choice. However, the conventional process requires high-temperature procedures that are incompatible with the production of flexible PSCs. Here, we specifically focus on the recent developments of the low-temperature process strategies for fabricating high-performance PSCs. This mini-review briefly discusses the development in low-temperature processed metal oxide and carbon-based electron extraction layer (EEL). The approaches for low-temperature solution-processed PSCs are introduced and then the various PSCs with distinctive EEL are discussed. Overall, this mini-review contributes to a better understanding of the low-temperature processed electron extraction layer. Strategies and perspectives are also provided for further high-performance PSCs.</p

Conjugated Polymer/Nanoparticles Nanocomposites for High Efficient and Real-Time Volatile Organic Compounds Sensors

The present work demonstrates a high efficient and low cost volatile organic compounds (VOCs) sensor. Nowadays, VOCs, which are typically toxic, explosive, flammable, and an environmental hazard, are extensively used in R&D laboratories and industrial productions. Real-time and accurately monitoring the presence of harmful VOC during the usage, storage, or transport of VOCs is extremely important which protects humans and the environment from exposure in case of an accident and leakage of VOCs. The present work utilizes conducting polymer/nanoparticles blends to sense various VOCs by detecting the variation of optical properties. The novel sensor features high sensitivity, high accuracy, quick response, and very low cost. Furthermore, it is easy to fabricate into a sensing chip and can be equipped anywhere such as a laboratory or a factory where the VOCs are either used or produced and on each joint between transporting pipes or each switch of VOC storage tanks. Real-time sensing is achievable on the basis of the instant response to VOC concentrations of explosive limits. Therefore, an alarm can be delivered within a few minutes for in time remedies. This research starts from investigating fundamental properties, processing adjustments, and a performance test and finally extends to real device fabrication that practically performs the sensing capability. The demonstrated results significantly advance the current sensor technology and are promising in commercial validity in the near future for human and environmental safety concerns against hazardous VOCs

Nitrogen Plasma Surface Modification of Poly(3,4-ethylenedioxythiophene):Poly(styrenesulfonate) Films To Enhance the Piezoresistive Pressure-Sensing Properties

A conductive polymeric film, poly­(3,4-ethylenedioxythiophene):poly­(styrenesulfonate) (PEDOT:PSS), is surface-modified by nitrogen plasma in order to enhance its piezoresistive characteristics. With an optimized 3 min nitrogen plasma surface modification, the piezoresistive sensitivity and response were significantly enhanced. Hall measurements and temperature-dependent conductance measurements are carried out to determine the electron-hopping behavior of nitrogen-plasma-modified PEDOT:PSS films, suppressing the horizontal carrier conducting pathway in the PEDOT:PSS piezoresistive pressure sensors. X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy are applied to observe the PEDOT:PSS film surface after being modified with nitrogen plasma. The presence of sulfamate (SO₃–NH₂) and thiocyanate (S–CN) groups indicates a breaking of the electrostatic bonding between PEDOT and PSS and a modification of the conductive PEDOT conjugated chain. At the film surface, the formation of thiocyanate groups of PEDOT oligomers without the electrostatic bonding of PSS makes the PEDOT:PSS more hydrophobic, changing the surface characteristics of the PEDOT:PSS film. The newly formed less-conductive film surface alters the piezoresistance of PEDOT:PSS pressure sensors, implying their potential applications for future high-performance tactile sensing

High-Sensitivity Raman Scattering Substrate Based on Au/La_0.7Sr_0.3MnO₃ Periodic Arrays

We have developed Au/La0.7Sr0.3MnO3 (Au/LSMO) periodic arrays with tunable surface plasmon properties that can be used as novel surface-enhanced Raman scattering (SERS) substrates. The periodic arrays are created by electron beam lithography of LSMO resist and metal film deposition. The LSMO electron beam resist is unique in that it exhibits either positive or negative resist behaviors depending on the electron beam dosage. Interestingly, surface plasmon behavior of the arrays can be controlled by just changing the electron beam dosage when presented with a fixed design pattern. Scanning confocal microscopy and spectral microreflectometry have been adapted to directly demonstrate this unique behavior. Furthermore, we show that our novel Au/LSMO array can be used as a high-sensitivity Raman scattering substrate. To illustrate this working principle, the Au/LSMO periodic array is applied to enhance the Raman scattering of a thin film containing 0.1 wt % poly-3-hexylthiophene (P3HT) in poly(methyl methacrylate) (PMMA). By controlling the geometry of the patterned substrate that exhibits gold surface plasmon near the excitation wavelength, we can enhance the intensity of Raman scattering of P3HT at 1350 cm−1 up to 4 orders of magnitude as compared with previously generated planar Au substrates

Effects of Gold Film Morphology on Surface Plasmon Resonance Using Periodic P3HT:PMMA/Au Nanostructures on Silicon Substrate for Surface-Enhanced Raman Scattering

We study the effects of the morphology of gold film on the unusual modulation of surface plasmon resonance (SPR) and surface-enhanced Raman scattering (SERS) using the periodic nanostructures of P3HT:PMMA/Au on the silicon substrate. The periodic structures of cylindrical holes with triangular lattice were fabricated first by e-beam lithography using a photoluminescent resist of P3HT:PMMA at a thickness of ∼100–200 nm, and the structures were then coated with gold of ∼20 nm thickness. The geometries and structures of the samples were studied by atomic force microscopy and scanning electron microscopy. The relationships between the geometry and the resonance were investigated by the extinction spectra and confocal Raman mapping. The results show that the resonance wavelength of the extinction peak is blue shifted, and its width becomes wider when the hole diameter of the structure increases or the lattice constant decreases. However, the extinction peak is red shifted when the thickness of the periodic nanostructures increases due to the surface plasmon resonance, localized surface plasmon resonances, and coupling between neighboring holes. The finite-difference time-domain (FDTD) method was adopted to simulate different nanostructures, and we found that the morphology and location of gold film on the periodic structure of P3HT:PMMA film played a vital role in the extinction spectra of the composite film of P3HT:PMMA/Au. A large enhancement of Raman scattering was observed when the SERS and SPR were correlated in the nanostructure at the exciting wavelength of 632.8 nm. This study provides a useful strategy to modulate the extinction spectra and enhance the intensity of Raman spectra by changing the nanostructures. The observed SERS will be useful for the design and fabrication of functional devices and sensors

Ultrasensitive Detection of Volatile Organic Compounds by a Freestanding Aligned Ag/CdSe–CdS/PMMA Texture with Double-Side UV–Ozone Treatment

Volatile organic compounds (VOCs) are organic chemicals having a high vapor pressure at room temperature. Chronic exposure to VOC vapor can be potentially dangerous to human health. In this study, we build a high-performance freestanding aligned Ag/CdSe–CdS/poly­(methyl methacrylate) (PMMA) texture to detect VOC vapors. The insight of this new VOC-sensing material is based on electrospinning techniques, ultraviolet (UV)/ozone treatments, and nano-optics. The incorporation of CdSe–CdS core–shell quantum rods (QR) and silver nanocrystals in the PMMA nanofibers amplifies the polarization response of long rods in VOC detection, thus increasing the sensitivity of VOC-sensing materials. Further, the uniaxial aligned Ag/QR/PMMA sensing material was treated by UV–ozone etching to increase surface absorption. The advanced double-sided UV–ozone etching on the uniaxial aligned Ag/QR/PMMA efficiently enhanced the extinction changes of VOCs. Two categories of solvents, typical VOCs and alcoholic VOCs, were put into practical tests for the Ag/QR/PMMA VOC-sensing materials. The Ag/QR/PMMA reached the detection limit for 100 ppm butanol within 1 min. The freestanding aligned Ag/CdSe–CdS/PMMA texture is a newly designed nanocomposite device for environmental risk monitoring. It can be accepted by the market compared to the other highly sensitive commercial VOC-sensing materials

Manipulation of Nanoscale Phase Separation and Optical Properties of P3HT/PMMA Polymer Blends for Photoluminescent Electron Beam Resist

A novel photoluminescence electron beam resist made from the blend of poly(3-hexylthiophene) (P3HT) and poly(methyl methacrylate) (PMMA) has been successfully developed in this study. In order to optimize the resolution of the electron beam resist, the variations of nanophase separated morphology produced by differing blending ratios were examined carefully. Concave P3HT-rich island-like domains were observed in the thin film of the resist. The size of concave island-like domains decreased from 350 to 100 nm when decreasing the blending ratio of P3HT/PMMA from 1:5 to 1:50 or lower, concurrently accompanied by significant changes in optical properties and morphological behaviors. The λmax of the film absorption is blue-shifted from 520 to 470 nm, and its λmax of photoluminescence (PL) is also shifted from 660 to 550 nm. The radiative lifetime is shorter while the luminescence efficiency is higher when the P3HT/PMMA ratio decreases. These results are attributed to the quantum confinement effect of single P3HT chain isolated in PMMA matrix, which effectively suppresses the energy transfer between the well-separated polymer chains of P3HT. The factors affecting the resolution of the P3HT/PMMA electron beam resists were systematically investigated, including blending ratios and molecular weight. The photoluminescence resist with the best resolution was fabricated by using a molecular weight of 13 500 Da of P3HT and a blending ratio of 1:1000. Furthermore, high-resolution patterns can be obtained on both flat silicon wafers and rough substrates made from 20 nm Au nanoparticles self-assembled on APTMS (3-aminopropyltrimethoxysilane)-coated silicon wafers. Our newly developed electron beam resist provides a simple and convenient approach for the fabrication of nanoscale photoluminescent periodic arrays, which can underpin many optoelectronic applications awaiting future exploration

Eco-Friendly Plasmonic Sensors: Using the Photothermal Effect to Prepare Metal Nanoparticle-Containing Test Papers for Highly Sensitive Colorimetric Detection

Convenient, rapid, and accurate detection of chemical and biomolecules would be a great benefit to medical, pharmaceutical, and environmental sciences. Many chemical and biosensors based on metal nanoparticles (NPs) have been developed. However, as a result of the inconvenience and complexity of most of the current preparation techniques, surface plasmon-based test papers are not as common as, for example, litmus paper, which finds daily use. In this paper, we propose a convenient and practical technique, based on the photothermal effect, to fabricate the plasmonic test paper. This technique is superior to other reported methods for its rapid fabrication time (a few seconds), large-area throughput, selectivity in the positioning of the NPs, and the capability of preparing NP arrays in high density on various paper substrates. In addition to their low cost, portability, flexibility, and biodegradability, plasmonic test paper can be burned after detecting contagious biomolecules, making them safe and eco-friendly

Miniaturized Flexible Piezoresistive Pressure Sensors: Poly(3,4-ethylenedioxythiophene):Poly(styrenesulfonate) Copolymers Blended with Graphene Oxide for Biomedical Applications

Piezoresistive pressure sensors have garnered significant attention because of their wide applications in automobiles, intelligent buildings, and biomedicine. For in vivo testing, the size of pressure sensors is a vital factor to monitor the pressure of specific portions of a human body. Therefore, the primary focus of this study is to miniaturize piezoresistive pressure sensors with graphene oxide (GO)-incorporated poly­(3,4-ethylenedioxythiophene):poly­(styrenesulfonate) (PEDOT:PSS) composite films on a flexible substrate for biomedical applications. Prior to the fabrication of pressure sensors, a comprehensive material analysis was applied to identify the horizontal placement of GO flakes within the PEDOT:PSS copolymers, revealing a reduction in variable range hopping distance and an enhancement in carrier mobility. For devices scaled to 0.2 cm, the sensitivity of PEDOT:PSS pressure sensors was conspicuously decreased owing to the late response, which can be effectively solved by GO incorporation. Using technology computer-aided design simulations, the current crowded at the PEDOT:PSS film surface and in the vicinity of an indium–tin–oxide electrode corner was found to be responsible for the changes in piezoresistive behaviors of the scaled devices. The miniaturized flexible piezoresistive pressure sensors with PEDOT:PSS/GO composite films are capable of monitoring the brain pressure of intracranial surgery of a rat and discerning different styles of music for a potential application in hearing aids

Nitrogen-Doped Anatase Nanofibers Decorated with Noble Metal Nanoparticles for Photocatalytic Production of Hydrogen

We report the synthesis of N-doped TiO2 nanofibers and high photocatalytic efficiency in generating hydrogen from ethanol–water mixtures under UV-A and UV-B irradiation. Titanate nanofibers synthesized by hydrothermal method are annealed in air and/or ammonia to achieve N-doped anatase fibers. Depending on the synthesis route, either interstitial N atoms or new N–Ti bonds appear in the lattice, resulting in slight lattice expansion as shown by XPS and HR-TEM analysis, respectively. These nanofibers were then used as support for Pd and Pt nanoparticles deposited with wet impregnation followed by calcination and reduction. In the hydrogen generation tests, the N-doped samples were clearly outperforming their undoped counterparts, showing remarkable efficiency not only under UV-B but also with UV-A illumination. When 100 mg of catalyst (N-doped TiO2 nanofiber decorated with Pt nanoparticles) was applied to 1 L of water–ethanol mixture, the H2 evolution rates were as high as 700 μmol/h (UV-A) and 2250 μmol/h (UV-B) corresponding to photo energy conversion percentages of ∼3.6 and ∼12.3%, respectively