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

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

Quantitative Nanoorganized Structural Evolution for a High Efficiency Bulk Heterojunction Polymer Solar Cell

We have developed an improved small-angle X-ray scattering (SAXS) model and analysis methodology to quantitatively evaluate the nanostructures of a blend system. This method has been applied to resolve the various structures of self-organized poly(3-hexylthiophene) /C61-butyric acid methyl ester (P3HT/PCBM) thin active layer in a solar cell from the studies of both grazing-incidence small-angle X-ray scattering (GISAXS) and grazing-incidence X-ray diffraction (GIXRD). Tuning the various length scales of PCBM-related structures by a different annealing process can provide a flexible approach and better understanding to enhance the power conversion of the P3HT/PCBM solar cell. The quantitative structural characterization by this method includes (1) the mean size, volume fraction, and size distribution of aggregated PCBM clusters, (2) the specific interface area between PCBM and P3HT, (3) the local cluster agglomeration, and (4) the correlation length of the PCBM molecular network within the P3HT phase. The above terms are correlated well with the device performance. The various structural evolutions and transformations (growth and dissolution) between PCBM and P3HT with the variation of annealing history are demonstrated here. This work established a useful SAXS approach to present insight into the modeling of the morphology of P3HT/PCBM film. In situ GISAXS measurements were also conducted to provide informative details of thermal behavior and temporal evolution of PCBM-related structures during phase separation. The results of this investigation significantly extend the current knowledge of the relationship of bulk heterojunction morphology to device performance

Nanoparticle-Tuned Self-Organization of a Bulk Heterojunction Hybrid Solar Cell with Enhanced Performance

We demonstrate here that the nanostructure of poly(3-hexylthiophene) and [6,6]-phenyl-C61-butyric acid methyl ester (P3HT/PCBM) bulk heterojunction (BHJ) can be tuned by inorganic nanoparticles (INPs) for enhanced solar cell performance. The self-organized nanostructural evolution of P3HT/PCBM/INPs thin films was investigated by using simultaneous grazing-incidence small-angle X-ray scattering (GISAXS) and grazing-incidence wide-angle X-ray scattering (GIWAXS) technique. Including INPs into P3HT/PCBM leads to (1) diffusion of PCBM molecules into aggregated PCBM clusters and (2) formation of interpenetrating networks that contain INPs which interact with amorphous P3HT polymer chains that are intercalated with PCBM molecules. Both of the nanostructures provide efficient pathways for free electron transport. The distinctive INP-tuned nanostructures are thermally stable and exhibit significantly enhanced electron mobility, external quantum efficiency, and photovoltaic device performance. These gains over conventional P3HT/PCBM directly result from newly demonstrated nanostructure. This work provides an attractive strategy for manipulating the phase-separated BHJ layers and also increases insight into nanostructural evolution when INPs are incorporated into BHJs

All-Polymer Solar Cell Performance Optimized via Systematic Molecular Weight Tuning of Both Donor and Acceptor Polymers

The influence of the number-average molecular weight (<i>M</i>_n) on the blend film morphology and photovoltaic performance of all-polymer solar cells (APSCs) fabricated with the donor polymer poly­[5-(2-hexyldodecyl)-1,3-thieno­[3,4-<i>c</i>]­pyrrole-4,6-dione-<i>alt</i>-5,5-(2,5-bis­(3-dodecylthiophen-2-yl)­thiophene)] (<b>PTPD3T</b>) and acceptor polymer poly­{[<i>N</i>,<i>N</i>′-bis­(2-octyldodecyl)­naphthalene-1,4,5,8-bis­(dicarboximide)-2,6-diyl]-<i>alt</i>-5,5′-(2,2′-bithiophene)} (P­(NDI2OD-T2); <b>N2200</b>) is systematically investigated. The <i>M</i>_n effect analysis of <i>both</i> <b>PTPD3T</b> and <b>N2200</b> is enabled by implementing a polymerization strategy which produces conjugated polymers with tunable <i>M</i>_ns. Experimental and coarse-grain modeling results reveal that systematic <i>M</i>_n variation greatly influences both intrachain and interchain interactions and ultimately the degree of phase separation and morphology evolution. Specifically, increasing <i>M</i>_n for both polymers shrinks blend film domain sizes and enhances donor–acceptor polymer–polymer interfacial areas, affording increased short-circuit current densities (<i>J</i>_sc). However, the greater disorder and intermixed feature proliferation accompanying increasing <i>M</i>_n promotes charge carrier recombination, reducing cell fill factors (<i>FF</i>). The optimized photoactive layers exhibit well-balanced exciton dissociation and charge transport characteristics, ultimately providing solar cells with a 2-fold PCE enhancement versus devices with nonoptimal <i>M</i>_ns. Overall, it is shown that proper and precise tuning of both donor and acceptor polymer <i>M</i>_ns is critical for optimizing APSC performance. In contrast to reports where maximum power conversion efficiencies (PCEs) are achieved for the highest <i>M</i>_ns, the present two-dimensional <i>M</i>_n optimization matrix strategy locates a PCE “sweet spot” at intermediate <i>M</i>_ns of both donor and acceptor polymers. This study provides synthetic methodologies to predictably access conjugated polymers with desired <i>M</i>_n and highlights the importance of optimizing <i>M</i>_n for <i>both</i> polymer components to realize the full potential of APSC performance

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