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Background Poly(3,4-ethylenedioxythiophene):poly-(styrenesulfonate) (PEDOT:PSS) is a promising conductive polymer for the flexible piezoresistive pressure sensor. However, intrinsic hydrophilicity is detrimental to its structural stability under moisture. The present study aims to enhance piezoresistive pressure sensors' stability to achieve the highly-reliable electronic device applications. Method ITO/PEDOT:PSS/ITO piezoresistive pressure sensors with an interdigitated electrode (IDE) structure and different metallic interfacial layers were fabricated. Au layer was introduced between PEDOT:PSS sensing membrane and indium tin oxide (ITO) electrode as a reaction-inhibited interfacial coating of piezoresistive pressure sensors. Significant findings After a measurement time interval of 6 months, the interface reaction suppressed significantly, resulting in low sensitivity deviation (9.22%) and improved durability (400 cycles). The devices are completely sealed using polyethylene terephthalate packaging, avoiding humidity absorption in PEDOT:PSS films successfully. The packaged ITO/PEDOT:PSS/ITO piezoresistive pressure sensors with a double-sided 10-nm-thick Au interfacial layer is a promising candidate for use in highly reliable pressure sensing applications.

Cancer metastasis involves not only cancer cells but also fibroblasts and the surrounding collagen matrices. Previous studies have reported that in tumor tissues, cancer cells and fibroblasts surrounded by dense collagen are often associated with a high risk of cancer metastasis. However, the mechanism of the interaction between the cancer cells, fibroblasts, and the surrounding collagen matrices

Perovskite solar cells (PSCs) have earned considerable attention and are candidates against the inevitable energy crisis. Even though various successful PSCs have emerged, increasing the PCE by reinforcing charge collection is still a critical issue. The manipulation of carriers between the perovskite active layer and the electron extraction layer (EEL) is essential. Here, we prepared a tin-doped TiO2 (Sn/TiO2) EEL that presented two main polymorphs, anatase and rutile, and successfully fabricated a high-performance planar PSCs. Besides, the band alignment between EEL and perovskite active layer could be optimized by tuning the Sn doping concentration and the ratio of anatase and rutile phases. The intrinsic conductivity, interface morphology, band alignment, and charge carrier dynamic were characterized and the relationship to the photovoltaic performance was clarified. As the Sn ions being doped into TiO2 structure, EEL presented the mixed TiO2 rutile/anatase phase, directly narrowing the bandgap and promoting mobility. Furthermore, the adjustment of the band structure can facilitate electronic transitions. Finally, a promising planar PSC with Sn/TiO2 phase junction EEL achieved a champion PCE of 15.4%.

Nowadays, a dye-sensitized solar cell (DSSC) attracts attention to its development widely due to its several advantages, such as simple processes, low costs, and flexibility. In this work, we demonstrate the difference in device structures between small size and large size cells (5 cm × 5 cm, 10 cm × 10 cm and 10 cm × 15 cm). The design of the photoanode and dye-sensitized process plays important roles in affecting the cell efficiency and stability. The effects of the TiO2 electrode, using TiCl4(aq) pretreatment and post-treatment processes, are also discussed, whereas, the open-circuit voltage (Voc), short-circuit current density (Jsc), and module efficiency are successfully improved. Furthermore, the effects on module performances by some factors, such as dye solution concentration, dye soaking temperature, and electrolyte injection method are also investigated. We have demonstrated that the output power of a 5 cm × 5 cm DSSC module increases from 86.2 mW to 93.7 mW, and the module efficiency achieves an outstanding performance of 9.79%. Furthermore, enlarging the DSSC modules to two sizes (10 cm × 10 cm and 10 cm × 15 cm) and comparing the performance with different module designs (C-DSSC and S-DSSC) also provides the specific application of polymer sealing and preparing high-efficiency large-area DSSC modules.

Organic-inorganic hybrid perovskite solar cells (PSCs), a superstar of photovoltaic devices, have attracted people’s attention owing to their adjustable energy band gap value, extremely high absorption coefficient, long charge carrier diffusion length, and dramatically high power conversion efficiency. In recent years, researchers have tried hard to explore new strategies in order to obtain better optical characteristics. Metal ion-doped electron transport layer (ETL) is a convenient way to improve the optical properties of PSCs. By this method, the conduction band and valence band position can be changed. This can lead to the carriers can effectively transport, and the charge recombination between ETL and absorber layer be reduced. In our study, we have enhanced the photovoltaic performance and the hysteresis behavior of the device by using various concentrations of mesoscopic Ag-doped TiO2 (meso-Ag:TiO2) as the ETL. We also systematically discussed the surface morphology, the charge carrier dynamic, the electron mobility, and the electrical conductivity for our devices. Finally, by optimizing the parameters of PSCs and the energy band alignment between perovskite absorber layer and ETL, the power conversion efficiency (PCE) of the champion device with 1.00 mol% meso-Ag:TiO2 ETL reached as high as 17.7%.

The rapid development of machine learning has proven its potential in material science. To acquire an accurate and promising result, the choice of descriptor plays an essential role in dictating the model performance. In this work, we introduce a set of novel descriptors, Element Code, which is generated from pseudopotential. Using a variational autoencoder to perform unsupervised learning, the produced Element Code is verified to contain representative information on elements. Attributed to the successful extraction of information from pseudopotential, Element Code can serve as the primary descriptor for the machine learning model. We construct a model using Element Code as the sole descriptor to predict the bandgap of a lead-free double halide perovskite, and an accuracy of 0.951 and mean absolute error of 0.266 eV are achieved. We believe our work can offer insights into selecting lead-free halide perovskites and establish a paradigm of exploring new materials.

Lead halide perovskite-structured solar cells (PSCs) have drawn great attention due to a rapid improvement in their photoelectric conversion efficiency in recent years. In this study, we have enhanced photovoltaic performance by using mesoscopic zinc-doped TiO2 (meso-Zn:TiO2) as the electron extraction layer. Zn:TiO2 nanoparticles (Zn:TiO2 NPs) with various zinc doping levels were synthesized by combining sol–gel and hydrothermal methods. The synthesized Zn:TiO2 NPs were used to fabricate electron extraction layers by a screen-printing method. We systematically investigated the surface morphology, crystal structure, contact angle, charge carrier dynamics, electron mobility, and electrical conductivity of various meso-Zn:TiO2. Furthermore, photo-assisted Kelvin probe force microscopy (KPFM) was used to analyze the surface potential of perovskite films coated with various meso-Zn:TiO2 to understand the electron extraction behavior under the illumination of light at various wavelengths. Moreover, the energy levels of various meso-Zn:TiO2 were estimated by ultraviolet photoelectron spectroscopy (UPS) and UV-vis absorption spectroscopy. We discovered that the 5.0 mol% meso-Zn:TiO2 exhibited the optimal band alignment with perovskite. Finally, the average power conversion efficiency (PCE) of PSCs with meso-Zn:TiO2 was enhanced from 13.1 to 16.8%, and such fabricated PSC yielded a champion PCE of 18.3%.

The continuous quest to enhance the output performance of triboelectric nanogenerators (TENGs) based on the surface charge density of the tribolayer has motivated researchers to harvest mechanical energy efficiently. Most of the previous work focused on the enhancement of negative triboelectric charges. The enhancement of charge density over positive tribolayer has been less investigated. In this work, we developed a layer-by-layer assembled multilayer graphene-based TENG to enhance the charge density by creatively introducing a charge trapping layer (CTL) Al2O3 in between the positive triboelectric layer and conducting electrode to construct an attractive flexible TENG. Based on the experimental results, the optimized three layers of graphene TENG (3L-Gr-TENG) with CTL showed a 30-fold enhancement in output power compared to its counterpart, 3L-Gr-TENG without CTL. This remarkably enhanced performance can be ascribed to the synergistic effect between the optimized graphene layers with high dielectric CTL. Moreover, the device exhibited outstanding stability after continuous operation of &gt, 2000 cycles. Additionally, the device was capable of powering 20 green LEDs and sufficient to power an electronic timer with rectifying circuits. This research provides a new insight to improve the charge density of Gr-TENGs as energy harvesters for next-generation flexible electronics.

Hybrid lead halide perovskite structured materials have created enormous expectations for low-cost and high-performance optoelectronic devices. The light-harvesting active layer of perovskite solar cell consists of hybrid organic-inorganic lead halide-based material. In this study, we successfully fabricated the perovskite photovoltaics with partial substitution of the lead cation (Pb 2+ ) with calcium ion (Ca 2+ ). The incorporation of Ca 2+ into the original structure was analyzed to observe the doping effect on the crystalline structure and the optical properties. Moreover, UV–vis spectra showed the decreased bandgap with ascending the dopants Ca 2+ amount. 1.0 mol% Ca-doped perovskite film has the lower emission energy, and it shows the low recombination behavior. After optimizing the perovskite solar cells, the V oc is increased from 0.93 to 0.98 V, the J sc is increased from 17.4 to 19.1 mA/cm 2 and the power conversion efficiency is enhanced from 10.7 to 12.9% by using 1.0 mol% Ca-doped perovskite material.

Organic–inorganic lead halide perovskite solar cells are considered as one of the most promising technologies for future photovoltaics because they show high power conversion efficiency (PCE) and can be fabricated through a simple solution process. Non-toxic alkaline-earth metal cations are suitable candidates to replace toxic lead in perovskite because they maintain the charge balance in perovskite and some of them meet the tolerance factor of Goldschmidt's rule. We investigated four kinds of alkaline-earth metal cations (Mg2+, Ca2+, Sr2+, and Ba2+) to replace lead cations partially. Among these four alkaline-earth metals, the Ba2+ is most suitable for Pb2+ replacement in perovskite films and exhibits the best power conversion efficiency. Furthermore, we systematically studied the crystal structure, absorption behavior and surface morphology of Ba2+-doped perovskite films with different doping levels. The relationship between the charge carrier dynamics and Ba2+ concentration was evaluated by the time-resolved photoluminescence (TRPL) technique. The Ba2+-doped perovskite films that can be processed in the environment containing moisture (1.0% relative humidity) are stable. At the optimal 3.0 mol% Ba2+ replacement, the PCE of the fabricated solar cell is increased from 11.8 to 14.0%, and the PCE of champion devices is as high as 14.9% with increased storage stability.

A carrier transport layer and its interfacial effects on an organometal halide perovskite light harvesting layer play an influential factor in either photovoltaic performance or long-term stability of a perovskite solar cell (OHPSC). Although the understandings of the carrier transport layers and interfacial effects on regular structured OHPSCs have been explored, knowledge of an interface between hole transport layer of NiOx and perovskite in an inverted OHPSC is still necessary to be developed. Here, we performed a universal NiOx film with the sequential passivation strategy of NiCl2 (SPS-NiCl2 treatment) for either wide bandgap or narrow bandgap of OHPSCs. The SPS-NiCl2 treated NiOx film not only implements the passivation at the perovskite layer/NiOx film interface but also confers itself a gradient energy level of valance band inducing by chloride. Comprehensive characterizations reveal that the SPS-NiCl2 treated NiOx film suppresses non-radiative recombination at the interface and enlarges the splitting of the quasi-Fermi level at the interfaces. The photoconversion efficiency (PCE) of the champion device comprised of the SPS-NiCl2 treated NiOx film can achieve 19.53% with a record Voc of 1.16 V, the lowest Voc deficit of 390 mV in NiOx based inverted OHPSCs. The corresponding devices with encapsulation also exhibit superior long-term stability, and over 80% of initial PCE can be maintained after 1500 h damp-heat test. This study sheds the light on managing the interfacial issues of an inverted OHPSC and offers a feasible path to develop a universal hole transport layer for perovskite layers with different energy bandgap.

Doping metal-ion into TiO 2 materials is an effective method for enhancing the performance of dye-sensitized solar cells (DSSCs). In order to develop materials that are easy to produce even in industrial quantities, we established a facile method by hydrothermal synthesis and subsequent heat treatment to prepare bismuth doped titanium dioxide nanofibers (Bi-doped TiO 2 NFs). At first, we adopt Bi-doped TiO 2 NFs as the working electrode to further study in DSSCs. Serving as working electrode, Bi-doped TiO 2 NFs can remarkably improve open-circuit voltage ( V OC ). The V OC was significantly enhanced from 0.633 V to 0.800 V compared with pristine TiO 2 does. However, this leads to a smaller J SC and a poorer overall performance for such devices. In order to improve the performance of DSSCs, we adopt Bi-doped TiO 2 NFs as the scattering layer of DSSCs, and various thicknesses of meso-TiO 2 nanoparticles (meso-TiO 2 NPs) were used as working electrode to increase the short-circuit current ( J SC ). The incorporated Bi-doped TiO 2 NFs can help the electron transport and may reduce the possibility for electron–hole recombination. After optimizing the device’s parameter, the overall performance of the meso-TiO 2 NPs/Bi-doped TiO 2 NFs devices was dominated by J SC until a maximum efficiency was attained with a meso-TiO 2 NPs thickness of 12 μm. Such optimized DSSCs exhibited high open circuit voltage of 0.787 V, high fill factor of 78.2%, and high power conversion efficiency of 8.89%.

Perovskite solar cells (PSCs) have become one of the most promising renewable energy converting devices. However, in order to reach a sufficiently high power conversion efficiency (PCE), the PSCs typically require a high-temperature sintering process to prepare mesostructured TiO2 as an efficient electron transport layer (ETL), which prohibits the PSCs from commercialization in the future. This work investigates a low-temperature synthesis of TiO2 nanocrystals and introduces a two-fluid spray coating process to produce a nanostructured ETL for the following deposition of perovskite layer. The temperature during the whole deposition process can be maintained under 150 °C. Compared to the typical planar TiO2 layer, the perovskite layer fabricated on a nanostructured TiO2 layer shows uniform compactness, preferred orientation, and high crystallinity, leading to reproducible and promising device performance. The detail mechanisms are revealed by the contact angle test, morphology characterization, grazing incident wide angle X-Ray scattering measurement, and space charge limited currents analysis. Finally, optimized device performance can be achieved through adequate Zn doping in the TiO2 layer, demonstrating an average PCE of 19.87% with champion PCE of 21.36%. The efficiency can maintain over 80% of its original value after 3000 h storage in ambient atmosphere. This study suggests a promising approach to offer high-efficiency PSCs using the low-temperature process.

Layer-dependent solvent vapor annealing (LDSVA) treatment using dimethylformamide (DMF) vapor on specific layers of stacked poly(vinylidenefluoride-co-trifluoroethylene) (P(VDF-TrFE)) copolymers by metal-ferroelectric-metal (MFM) capacitors and nanogenerators was investigated in this study. Prior to the fabrication of the devices, X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, and scanning electron microscopy (SEM) were performed to analyze the polarization of the crystalline β-phase in LDSVA-treated stacked P(VDF-TrFE) copolymers. After the LDSVA treatment on the top and bottom of the stacked films, the ferroelectric properties of P(VDF-TrFE) MFM capacitors became asymmetric. This can be confirmed via the bias electric field (Ebias) and non-switchable leakage current due to the non-uniform distribution of polarized dipoles. With an increase in LDSVA treatment time, the arrangement of polarized dipoles in stacked P(VDF-TrFE) copolymers was significantly enhanced, especially the samples with the treatment on the bottom of the stacked films, contributing to a large remnant polarization (2Pr) and a low coercive electric field (Ec) of the MFM capacitors. Additionally, the piezoelectric nanogenerators with LDSVA treatment on stacked P(VDF-TrFE) copolymers presented a large open-circuit output voltage of more than 4.02 V at 7 Hz under an applied force of 800 g, which is approximately 3 times larger than that of the samples without treatment. The LDSVA-treated stacked P(VDF-TrFE) copolymers with superior ferroelectric and nanogenerator behaviors exhibit good potential with regard to highly efficient energy harvesting applications.

Piezoelectric pressure sensing behaviors of high-density and low-damage CF4-plasma-treated indium gallium zinc oxide (IGZO) thin-film transistors (TFTs) coated by poly(vinylidene fluoride-co-trifluoroethylene) (P(VDF-TrFE)) films have been investigated. The CF4 plasma treatment was performed on the IGZO channel by using an inductively coupled plasma (ICP) system with a quartz filter. Prior to the fabrication of devices, X-ray diffractometer (XRD) and atomic force microscopy (AFM) were applied to identify the enhancement in the crystallinity of P(VDF-TrFE) films on the plasma-fluorinated IGZO films. With the analyses of X-ray photoelectron spectroscopy (XPS), it is proved that the fluorine radicals reacted with the metal-oxygen bonds will increase the oxygen vacancies in IGZO films, contributing to an enhancement in field effect mobility (μFE) and drain current (IDS) of IGZO TFTs. Furthermore, the fluorine atoms diffused from the IGZO channel into the bottom SiO2 layer were confirmed by secondary ion-mass spectroscopy (SIMS), reducing the interfacial and oxide charges of the devices for a negative shift in threshold voltage (Vt). Under a 0.5-kg applied force press/release cyclic test, a 4.8-fold increase in drain current response of 1-min CF4-plasma-treated piezoelectric pressure sensors was optimized, because of the enhanced electrical behaviors of IGZO TFTs and an increase in aligned dipole moments of P(VDF-TrFE) copolymers. The promising results make the piezoelectric pressure sensors with high-density and low-damage CF4-plasma-treated IGZO TFTs coated by P(VDF-TrFE) copolymer suitable for future high-performance tactile sensing applications.

This study demonstrates the effect of electron collection and transportation for TiO2 electron transport layer (ETL) of the mesoscopic perovskite solar cells (PSCs). The influence of compact TiO2 layer (c-TiO2) with various spray cycles, the particle size effect of mesoporous TiO2 (meso-TiO2) film and post-treatment of TiO2 electrode for perovskite solar cells have been studied systematically. We further optimize the meso-TiO2 thickness to enhance the electron collection and transport efficiency and to reduce the anomalous J-V hysteresis phenomenon of PSCs. After adjusting the fabrication process of TiO2 ETL, the highest performance of small cell PSC shows the power conversion efficiency (PCE) of 19.39% in the reverse scan and 19.12% in the forward scan, respectively. A sub-module PSC within an active area of 11.7 cm2 exhibits impressive PCE of 16.03% under the illumination of 100 mW/cm2 (AM1.5G). Moreover, it also shows an outstanding PCE of 25.49% under the illumination of 6000 lx of T5 indoor light source.

Solution-processed zinc oxide (ZnO)-based planar heterojunction perovskite photovoltaic device is reported in this study. The photovoltaic device benefits from the ZnO film as a high-conductivity and high-transparent electron transport layer. The optimal electron transport layer thickness and post-baking temperature for ZnO are systematically studied by scanning electron microscopy, photoluminescence and time-resolved photoluminescence spectroscopy, and X-ray diffraction. Optimized perovskite solar cells (PSCs) show an open-circuit voltage, a short-circuit current density, and a fill factor of 1.04 V, 18.71 mA/cm2, and 70.2%, respectively. The highest power conversion efficiency of 13.66% was obtained when the device was prepared with a ZnO electron transport layer with a thickness of ~20 nm and when post-baking at 180 °C for 30 min. Finally, the stability of the highest performance ZnO-based PSCs without encapsulation was investigated in detail.

Bernal- and rhombohedral-stacked trilayer graphene (B- and r-TLG) on nickel (Ni) and iridium (Ir) films acting as bottom electrodes (BEs) of silver electrochemical metallization cells (Ag-EMCs) have been investigated in this study. Prior to the fabrication of the EMC devices, Raman mapping and atomic force microscopy are applied to identify the B- and r-TLG sheets, with the latter revealing a significant D peak and a rough surface for the Ir film. The Ag-EMCs with the stacked BE of r-TLG on the Ir film show a conductive mechanism of Schottky emission at the positive top electrode bias for both high- and low-resistance states that can be examined by the resistance change with the device area and are modulated by pulse bias operation. Thus, an effective electron barrier height of 0.262 eV at the r-TLG and Ir interface is obtained because of the conspicuous energy gap of r-TLG on the Ir film and the van der Waals (vdW) gap between the r-TLG and Ir contact metal. With the use of Ni instead of Ir contact metal, the Ag-EMCs with TLG BE demonstrate +0.3 V/-0.75 V operation voltages, more than 10

In this study, the cross-talk effects and the basic piezoresistive characteristics of gold nanoparticle (Au-NP) incorporated poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) pressure sensing 2 × 2 arrays are investigated using a cross-point electrode (CPE) structure. Transmission electron microscopy (TEM), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS) mappings were carried out to confirm the incorporation of Au-NPs in the PEDOT:PSS films. A solution mixing process was employed to incorporate the nanoparticles. When the diameter of the Au-NPs incorporated in the PEDOT:PSS films (Au-NPs/PEDOT:PSS) was 20 nm, the piezoresistive pressure sensing 2 × 2 arrays were almost immune to cross-talk effects, which enhances the pressure sensing accuracy of the array. The Au-NPs render the PEDOT:PSS films more resilient. This is confirmed by the high plastic resistance values using a nanoindenter, which reduce the interference between the active and passive cells. When the size of the Au-NPs is more than 20 nm, a significant cross-talk effect is observed in the pressure sensing arrays as a result of the high conductivity of the Au-NPs/PEDOT:PSS films with large Au-NPs. With the incorporation of optimally sized Au-NPs, the PEDOT:PSS piezoresistive pressure sensing arrays can be promising candidates for future high-resolution fingerprint identification system with multiple-electrode array structures.

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 P3...

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 lambda(max) of the film absorption is blue-shifted from 520 to 470 nm, and its lambda(max) 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.

We have developed Au/La(0.7)Sr(0.3)MnO(3) (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.

We have studied the effect of annealing process on the performance of photovoltaic devices based on the bulk heterojunction of poly(3-hexylthiophene) and [6,6]-phenyl-C 61 butyric acid methyl ester (P3HT/PCBM). By means of atomic force microscopy (AFM) and scanning of near-field microscopy (SNOM), we can observe the morphology evolution of the annealed P3HT/PCBM composite films. We also studied the changes of optical properties by absorption spectroscopy and the changes of composition distribution of annealed composite films. The results indicate the P3HT in the composite film gradually becomes an ordered structure with annealing. The ordered P3HT facilitates the charge transport. However, the film exhibits a large-scale (1 μm) PCBM aggregation after annealing for an extended period of time. The disrupted bi-continous phase retards the charge transport. Thus, the device efficiency reaches the highest (2.308%) after annealing at 140 °C for 30 min but decreases to 0.810% after 60 min annealing.

We have fabricated a photovoltaic (PV) device based on the polymer blends of (poly(3-hexylthiophene) (P3HT)/polymethylmethacrylate (PMMA)) and inorganic TiO 2 nanorod bulk heterojunction. The optimized photovoltaic device with 1.6 wt% PMMA concentration has a power conversion efficiency of 0.65% under simulated AM 1.5 illumination (100 mW/cm 2 ), which is 38% more efficient than the device without the incorporation of PMMA. Furthermore, the PMMA-included device gives a short-circuit current density of 2.57 mA/cm 2 , an open-circuit voltage of 0.53 V, and a fill factor of 0.48. Our studies have shown that having optimal PMMA concentration in the photovoltaic devices helps to smoothen the surface of the hybrid thin film, broaden the absorption spectrum, and improve the electrical conductivity. The results implying improvement in cell performance can be illustrated using atomic force microscopy (AFM), a UV/vis spectrophotometer and electrical measurements.

We have investigated the enhancement of light absorption and carrier transport of poly(3-hexylthiophene) (P3HT) resulted from doping with multi-wall carbon nanotubes (MWNTs). The MWNTs were acid washed first, and then incorporated into P3HT homogenously. The MWNTs make P3HT unfolded with more alignment and thus increase light absorption as shown by the studies of AFM and UV–vis spectroscopy. The KFM data provides useful information to differentiate the work function of the MWNTs from P3HT and further show improved hole transporting behaviors. Based upon these results, the 0.01 wt% MWNTs doped P3HT/PCBM photovoltaic device shows an increase of 29% power conversion efficiency.

ARTICLE I NFO We have fabricated an arrayed CdSe quantum dots composite thin film that can enhance the photo- luminescence of CdSe under the 488 nm laser irradiation by tuning the gold surface plasmon resonance frequency. This thin film consists of a gold coated periodic array of hybrid material of CdSe and poly(methyl methacrylate) on indium tin oxide coated glass substrate. The main surface plasmon resonance was red shifted as we increased the column diameter of the array. By adjusting the column diameters and lattice constants of the array to coincide with the 488 nm excitation wavelength, an evident increase in luminescence intensity was obtained due to the surface plasmon resonance of gold. As a result of likely efficient energy transfer from gold surface plasmon resonance to CdSe, the photoluminescence intensity of CdSe has been increased to 248% at 570 nm. This composite film has many potential applications in high efficient optoelectronic devices.

A dual functional and water soluble spin-coatable lanthanum strontium manganese oxide (LSMO) resist has been developed that consists of lanthanum nitrate, strontium nitrate, manganese nitrate, polyvinyl alcohol and water. Energetic nitrates plus polyvinyl alcohol fuel promote autoignition and produce nanopatterns (

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.

Many organic/inorganic nanocomposites have been fabricated into fibrous materials using electrospinning techniques, because electrospinning processes have many attractive advantages and the ability to produce relatively large-scale continuous films. In this study, the polyvinyl alcohol (PVA)/silk/titanium dioxide ( TiO 2) nanocomposite self-cleaning textiles were successfully produced using electrospinning technique. After optimizing electrospinning conditions, we successfully obtained the PVA/silk/ TiO 2 nanocomposite fibers with average diameter of ∼220 nm and TiO 2 concentration can be as high as 18.0 wt.%. For the case of the PVA/silk/ TiO 2 nanocomposite textile, the color of brilliant green coated on the textile surface changed from the initial green color to colorless after ultraviolet (UV) irradiation. Because of its worthy photocatalytic performance, the developed PVA/silk/ TiO 2 nanocomposite materials in this study will be beneficial for the design and fabrication of multifunctional fibers and textiles.

An optically bandpass filtered SOA-EDFL laser link with suppressed phase noise of -110 dBc/Hz and improved supermode noise suppression ratio of 90 dB after harmonic mode-locking and fiber-based pulse compression (to 3.1 ps) are demonstrated.

The variations and trade-off between single-sided-band (SSB) phase noise and supermode noise (SMN) suppression ratio of an actively mode-locked erbium-doped fiber laser (EDFL) with intra-cavity semiconductor optical amplifier (SOA) based high-pass filter are discussed. The insertion of an SOA increases the SMN suppression ratio of the EDFL from 26 dB to 41.4 dB, however, the SSB phase noise at 100 kHz offset frequency from carrier is concurrently degraded from -114 dBc/Hz to -96 dBc/Hz. Such an operation also causes a broadening in the EDFL pulsewidth from 36 ps to 130 ps. The insertion of an optical bandpass filter (OBPF) further reduces the SSB phase noise to -110 dBc/Hz and improves the SMN suppression ratio to 43 dB. Theoretical simulation interprets that the optimized operation of the SOA based high-pass filter at nearly transparent current condition is mandatory to achieve a better SMN suppression ratio and minimize the SSB phase noise of the mode-locked EDFL without sacrificing its output pulsewidth.

We compare the noise characteristics of optical pulses generated from an actively mode-locked (AML) erbium-doped fiber laser (EDFL) with a semiconductor optical amplifier and an injection-locked EDFL with a gain-switched FabryPerot laser diode (FPLD). The mode-locked EDFL pulse exhibits a phase noise of -110.1 dBc/Hz (at 1 MHz offset frequencies from the carrier), the timing jitter of 1.16 ps, and a supermode noise suppression ratio of 47.5 dB. The injection-locked EDFL pulse exhibits a phase noise of -121.1 dBc/Hz (at 1 MHz offset frequencies from the carrier), a timing jitter of 0.31 ps, and a supermode noise suppression ratio of 51 dB. It is demonstrated that the injection-locked EDFL with a gain-switched FPLD has lower noise characteristics than the AML-EDFL.

The variations and trade-off between the single side band phase noise, supermode noise suppression ratio and pulsewidth of a mode-locked erbium-doped fiber laser with an intra-cavity semiconductor optical amplifier based high-pass filter are discussed.

Copper–zinc–tin–chalcogenide (CZTSSe) with earth abundant elements has attracted increasing attention due to large absorption coefficient and band gap of ∼1.5 eV which is near the optimum band gap of single-junction photovoltaic devices. In this study, we used commercially available precursors to produce wurtzite Cu2ZnSnS4 nanocrystals by simple solvothermal synthesis. Different from the typical kesterite or stannite phases of CZTS, the nanocrystals synthesized in this study are in wurtzite phase with hexagonal crystal cell. The n-dodecanethiol was used to control the reactivity of metal ions, leading to the controlled size of CZTS nanoparticle by simply varying the reaction time. Furthermore, the as synthesized CZTS nanocrystals have novel wurtzite crystal structure. As a result, a red shift of absorption band edge between the CZTS nanoparticles with different size was obtained. Our study provides an extending method of CZTS nanocrystal ink preparation awaiting for further photovoltaic device application.

Bismuth sulfide (Bi2S3) nanorods exhibit a low band gap, a high absorbance coefficient and good dispersity. In this study, the synthesis conditions of Bi2S3 nanorods were systematically investigated to obtain nanorods of a desired dimension, with high aspect ratios and good crystallinity. The as synthesized Bi2S3 nanorods, 37.2 nm in length and 6.1 nm in width, have a low band gap of ∼1.4 eV with a conduction band and valence band of −3.8 eV and −5.2 eV, respectively. The nanorods were blended with poly(3-hexylthiophene) (P3HT) at a weight ratio of 1:1 to form a light harvesting P3HT:Bi2S3 hybrid film. The incorporated Bi2S3 nanorods can not only contribute light harvesting but also lead to a more ordered structure of the P3HT phase and a more efficient π–π* transition. Surface potential mapping of the hybrid film, measured by Kelvin probe force microscope (KPFM), shows a significantly negative shift (−34 mV) under white light illumination, which indicates carrier dissociation and the accumulation of negative charge on top of the hybrid film. The photovoltaic characteristics of the devices were also observed for those based on the P3HT:Bi2S3 hybrid film. This novel P3HT:Bi2S3 hybrid material provides a new candidate for the fabrication of low-cost and environmentally friendly polymer/inorganic hybrid solar cells.

We demonstrate experimentally an air-slot mode-gap photonic crystal cavity with quality factor of 15,000 and modal volume of 0.02 cubic wavelengths, based on the design of an air-slot in a width-modulated line-defect in a photonic crystal slab. The origin of the high Q air-slot cavity mode is the mode-gap effect from the slotted photonic crystal waveguide mode with negative dispersion. The high Q cavities with ultrasmall mode volume are important for applications such as cavity quantum electrodynamics, nonlinear optics and optical sensing., Comment: 12 pages, 4 figures

This is an in depth study on the surface potential changes of P3HT/TiO(2) nanorod bulk heterojunction thin films. They are affected by interlayer structures, the molecular weight of P3HT, the processing solvents and the surface ligands on the TiO(2). The addition of an electron blocking layer and/or the hole blocking layer to the P3HT/TiO(2) thin film can facilitate charge carrier transport and result in a high surface potential shift. The changes in surface potential of multilayered bulk heterojunction films are closely correlated to their power conversion efficiency of photovoltaic devices. Changing ligand leads to the largest change in surface potential yielding the greatest effect on the power conversion efficiency. Merely changing the P3HT molecular weight is less effective and varying the processing solvents is least effective in increasing power conversion efficiency. The steric effect of the ligand has a large influence on the reduction of charge carrier recombination resulting in a great effect on the power conversion efficiency. By monitoring the changes in the surface potential of bulk heterojunction film of multilayer structures, we have obtained a useful guide for the fabrication of high performance photovoltaic devices.

It is demonstrated that magnetic periodic arrays can be easily fabricated from direct writing water developable La0.7Sr0.3MnO3 electron beam resist. Two unique features of our approach are (1) the patterned La0.7Sr0.3MnO3 resist film can be developed using nontoxic and environmentally friendly pure water and (2) either positive or negative patterns can be fabricated depending on the dosage of electron beam. The mechanism of the dual function characteristic of the resist was studied using Kelvin probe microscope. The surface potential of patterned La0.7Sr0.3MnO3 resist increases with increasing electron beam dosage due to the changes of resist composition. The formations of periodic magnetic arrays were confirmed by the studies of scanning electron microscope and magnetic force microscope. The magnetization of La0.7Sr0.3MnO3 can be enhanced by postsintering the sample at 900 °C after electron beam irradiation. We have therefore provided a one-step, simple, and convenient alternative technique for the fabri...

In this study, polarized-Raman scattering measurements of an individual ZnO nanorod were carried out by using a confocal microscope together with a high-resolution piezoelectric stage. A predominant A1 (TO) mode at 378cm−1 in the parallel polarization (E∥) configuration and a predominant E2 (high) mode at 438cm−1 in the perpendicular polarization (E⊥) configuration demonstrate the strong polarization dependent Raman scattering signals of an individual ZnO nanorod. The Raman intensity images of the individual ZnO nanorods with different orientation configurations can also be obtained, which reflect the interplay between the local phonon behavior and geometric anisotropy.

We have investigated the effect of polymer molecular weight on the morphology and performance of poly(3-hexylthiophene)/TiO2nanorod hybrid photovoltaic devices by using scanning near field optical microscopy (SNOM), atomic force microscopy (AFM) and confocal Raman microscopy. From the topography and absorption mapping images, it is found that the rod-like structure of the low molecular weight polymer hybrid film consists of a large amount of grain boundaries and has a less continuous absorption mapping image. In contrast, the larger domain structure of the high molecular weight polymer hybrid film exhibits a continuous absorption mapping image, as a result of enhanced polymer stacking and electronic delocalization. The nanoscale morphology of the hybrid samples with different molecular weights also reveals the nature of photovoltaic performance and carrier transport behavior investigated by the time-of-flight technique.

We have fabricated a unique periodic structure with different optical properties in the visible range using a water-developable La0.7Sr0.3MnO3 electron beam resist. The La0.7Sr0.3MnO3 resist can be developed under a nontoxic and environmentally friendly manner using pure water. Additionally, the resist is capable of exhibiting both positive and negative resist behavior depending on the electron beam dosage. Thus, these special characteristics were used to fabricate and tune periodic structure thin films having controlled optical reflectance properties in the wavelength range of 300 nm to 800 nm with one fixed design electron beam pattern (i.e. without changing the geometries and lattice constants of the periodical structures) by simply changing the electron beam dosage only.

We have fabricated a composite thin film that exhibits intense photoactivated fluorescence of silver oxide at 522 and 529nm under the irradiation of a 488nm laser. This film consists of a silver coated polymeric periodic array on indium tin oxide glass substrate. By adjusting the column diameters and lattice constants of the array to coincide with the excitation wavelength, an order increase in fluorescence intensity was obtained due to the surface plasmon polariton resonance of silver. This composite film has many potential applications in highly efficient optoelectronic devices.

By operating an intracavity semiconductor-optical-amplifier- (SOA-) based high-pass filter at the nearly transparent current condition, the supermode noise (SMN), the relaxation oscillation, and the single-sideband (SSB) phase noise can be simultaneously suppressed in an actively mode-locked erbium-doped fiber laser (EDFL). The SOA at the nearly transparent condition enhances the SMN suppression ratio of the EDFL from 32 to 76 dB at the cost of the phase noise degrading from -114 to -104.2 dBc/Hz and broadening the pulse width from 36 to 61 ps. With an optical bandpass filter, the SSB phase noise and the SMN suppression ratio can be further improved to -110 dBc/Hz and 81 dB, respectively. The EDFL pulse can be further shortened to 3.1 ps with a time-bandwidth product of 0.63 after compression.

Optically harmonic mode-locking of a semiconductor optical amplifier fiber laser (SOAFL) induced by backward injecting a dark-optical comb is demonstrated for the first time. The dark-optical comb with 60-ps pulsewidth is generated from a Mach-Zehnder modulator, which is driven by an electrical comb at a DC offset of 0.3Vπ. Theoretical simulation indicates that the backward injection of dark-optical comb results in a narrow gain window of 60 ps within one modulating period, providing a cross-gain-modulation induced mode-locking in the SOAFL with a shortest pulsewidth of 15 ps at repetition frequency of 1 GHz. The mode-locked SOAFL pulsewidth can be slightly shortened to 10.8 ps with a 200m-long dispersion compensating fiber. After nonlinearly soliton compression in a 5km-long single mode fiber, the pulsewidth, linewidth and time-bandwidth product become 1.2 ps, 2.06 nm and 0.31, respectively.

Backward-optical-injection mode-locking of a semiconductor optical amplifier fiber laser with a 60-ps optical comb-like dark pulse-train is demonstrated with pulsewidth, linewidth and time-bandwidth product of 1.8 ps, 2.08 nm and 0.47, respectively, after dispersion compensation.