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In recent years, several strategies have been proposed and demonstrated to enhance the efficiency of organic light-emitting diodes (OLEDs) and organic photovoltaics (OPVs). In both types of devices, poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) is commonly used to enhance hole injection. The layer is further designed by incorporating metallic-based, carbon-based, organic, inorganic, and hybrid nanoparticles with the aim of improving the performance and hence the efficiency through the improvement of light out-coupling in OLEDs and enhancement in light absorption generation of hole-charge carriers in OPVs. This review elucidates the use of different types of nanoparticles that are doped into PEDOT:PSS and their effects on OLEDs or OPVs. The effects include surface plasmon resonance (SPR), scattering, better charge transport, improvement in surface morphology and electrical properties of PEDOT:PSS. Promising results have been obtained and can potentially lead to low cost, large-area manufacturing process.

Single layer organic light emitting diode (OLED)devices based on poly{[2-methoxy-5-(-2ethylhexyloxy)-1,4-phenylene]vinylene}(MEH-PPV)are fabricated and studied in this work .There are several factors that affect the performance of the fabricated OLED samples. Some of these factors are related to the fabrication parameters chosen for the OLED fabrication process. The effect of concentration and annealing temperature are investigated. Other environmental factors such as humidity or temperature affect the performance of fabricated OLED samples under long term exposure. An internet of things environment monitoring system (IoT-EMS) is developed to monitor and study the effect of these factors on the performance of the OLED samples. Exposure to humidity is found to severely degrade the samples. In summary, the optimum concentration for MEH-PPV is concluded to be4 mg/ml, and the best annealing temperature is 90C in this study. It is also deduced that humidity of 72-75% caused degradation of the samples in less than 20 hours.

A battery–supercapacitor hybrid energy storage system is investigated as a solution to reduce the high-power delivery stress on the battery. An optimally-sized system can further enhance the storage and cost efficiency. This paper discusses several possible problems in the sizing of a battery–supercapacitor hybrid energy storage system for practical applications. A sizing method that utilises data collected from a fully active embedded control hybrid energy system is proposed. The feasibility of the method is then tested on three load profiles that represent the load demand of inter- and intra-applications with a battery–supercapacitor hybrid energy storage system. The result is compared to a battery-only single energy storage system. The results verified that the number of batteries required in the hybrid energy storage system is reduced by at least 50% compared to the battery-only single energy storage system.

Electrochemical cell for energy storage such as battery and supercapacitor are developing rapidly in recent years. Battery has high specific energy but moderate to low cyclic rate and long recharge time. On the other hand, electrostatic double-layered capacitors (EDLC) is characterized by their extremely fast charge and discharge capability, high power density but relative low energy density. The limitation can be mitigated by having a hybrid of theses energy storage system which is synchronized in accordance to the application. In this work, the characteristics of a EDLC and lead acid battery are characterized and modelled using MATLAB®. Subsequently, a hybrid energy system consists of a combination of (EDLC) and battery is studied. From the model, an energy management scheme is implemented by using an embedded system to manage the charge-discharge rate, to ensure it operate within the safety envelope and maximised operation lifespan.

In this work, a water/alcohol-soluble conjugated polymer poly [(9,9-bis(3′-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9–dihexylfluorene)] (PFNC6) is synthesized and the photophysical properties are investigated. Subsequently, it is tested as electron injection layer in a blue emitting OLED with PFO. The maximum current efficiency (CE) and external quantum efficiency (EQE) of the device increased by 3 times to 0.75 cd/A and 0.66%. Further enhancement in the OLED performance is obtained when a bilayer electron injection consisting of PFNC6 and LiF are used where the maximum CE is 2.16 cd/A and the maximum EQE is 1.55%. Measurement with electron-only-devices confirmed that the electron mobility is increased for the device with PFNC6 as compared to the control device. Furthermore, higher Vbi is obtained in photovoltaic measurement when PFNC6 is used. As a result, the electron injection barrier is reduced and electron injection is more efficient.

The plasma characteristics of 355 nm and 532 nm laser ablation of Al-doped ZnO (AZO) target were studied by optical emission spectroscopy and ion probe measurements. Zn emission lines were measured detected at above 0.9 J/cm 2 for 355 nm laser and 0.6 J/cm 2 532 nm laser respectively, while Al species were detected only above 2 J/cm 2 . The kinetic energy of the ions was slightly higher for 532 nm ablation as compared to 355 nm ablation. In addition, the ablation of 532 nm laser was affected by the large laser penetration depth. When deposited at 2 and 4 J/cm 2 , AZO films with energy band gap of 3.45–3.6 eV were obtained. Nanostructured AZO films were obtained by 355 nm laser ablation but nano and micro-particulates were formed in 532 nm laser ablation. The large micron-sized particulates were Al-rich thus affecting not only the morphology but also the stoichiometry of the films. It is thus concluded that despite a lower ablation and growth rate, 355 nm generated Zn, O and also Al species at lower threshold fluence that can lead to high quality AZO films at room temperature.

The plasma that accelerates and compresses in the formation of the pinch in dense plasma focus devices has been found to be an abundant source of multiple radiations like ion beams and x-rays. In this work, the ion beam and x-ray emissions from a 2.7 kJ (13.5 kV, 30 µF) plasma focus device operated at pressure below 1 mbar were investigated. The time profile of the ion beam emission was analysed from the simultaneously measured ion beam, soft and hard x-ray signals using biased ion collectors, BPX 65 silicon PIN diode and a scintillator-photomultiplier tube assembly. Time resolved analysis of the emissions revealed that the emission of the ion beam corresponded to several different pinching instances. Two components of the ion beam were identified. An ion beam of lower energy but higher intensity was emitted followed by an ion beam of higher energy but lower intensity in the first plasma pinch. The ion beam emitted from the first plasma pinch also has higher energy than subsequent plasma pinches. The emission was found to be associated with the amplitude of voltage spike. The results from ion beam and electron beams suggest that they were emitted by the same localized electric field induced in the pinched plasma. The strongest plasma focus discharge indicated by sharp voltage spike of high amplitude and highest ion beam energy were both observed at 0.2 mbar. The average energy of the ion beam obtained is (53 ± 13) keV. At this optimum condition, the ions beam with the highest energy also led to the highest hard x-ray emission.

Background gases (O2, He or Ar) with the pressure from ~ 10−3 Pa to 133.3 Pa are used in 355 nm laser deposition of Al-doped ZnO at room temperature. The effects of these gases and pressure on plasma formation are studied by optical emission spectroscopy (OES) and time of flight (TOF) measurement. The OES results show that the emission intensity of the species in O2 and Ar decrease slightly and then increase exponentially above ~ 5 Pa. The emission intensity in Ar is the highest, followed by emission in O2 whilst the emission in He is low and weakly depend on background gas pressure. TOF measurements indicate that the ion velocity decrease with increasing O2 and Ar pressure at about 5–10 Pa. The ion velocity is highest in He while the ion velocities in O2 and Ar are similar. Thin-film samples deposited in different gas at 2.6 Pa are amorphous, but those deposited at 133.3 Pa are crystalline and exhibit different morphologies and optical properties depending on type of gas. Samples deposited in O2 are highly transparent but those deposited in He and Ar contain nano and micron-sized structures with

In this work, we investigated on the growth of Cu 2 ZnSnS 4 films by using pulsed Nd:YAG laser (355 nm) ablation of a quaternary Cu 2 ZnSnS 4 target. Depositions were performed at laser fluence from 0.5 to 4 J cm −2 . The films were grown at substrate temperature from 27 °C to 300 °C onto glass and silicon substrates. The dependence of the film morphology, composition, and optical properties are studied and discussed with respect to laser fluence and substrate temperature. Composition analysis from energy dispersive X-ray spectral results show that CZTS films with composition near stoichiometric were obtained at an optimized fluence at 2 J cm −2 by 355 nm laser where the absorption coefficient is >10 4 cm −1 , and optical band gap from a Tauc plot was ∼1.9 eV. At high fluence, Cu and Sn rich droplets were detected which affect the overall quality of the films. The presence of the droplets was associated to the high degree of preferential and subsurface melting on the target during high fluence laser ablation. Crystallinity and optical band gap (1.5 eV) were improved when deposition was performed at substrate temperature of 100 °C.

Nanostructured diamond-like carbon (DLC) films instead of the ultrasmooth film were obtained by pulsed laser ablation of pyrolytic graphite. Deposition was performed at room temperature in vacuum with substrates placed at off-axis position. The configuration utilized high density plasma plume arriving at low effective angle for the formation of nanostructured DLC. Nanostructures with maximum size of 50 nm were deposited as compared to the ultrasmooth DLC films obtained in a conventional deposition. The Raman spectra of the films confirmed that the films were diamond-like/amorphous in nature. Although grown at an angle, ion energy of >35 eV was obtained at the off-axis position. This was proposed to be responsible for subplantation growth of sp3hybridized carbon. The condensation of energetic clusters and oblique angle deposition correspondingly gave rise to the formation of nanostructured DLC in this study.

Al-doped ZnO (AZO) thin films were deposited on p-Si (100) by pulsed laser deposition from a composite ceramic target (ZnO:Al2O3) by using 355 nm laser at different O2 background pressure and substrate temperature. Upon ablation at laser fluence of 2 Jcm−2, plasma plume consists of Zn neutrals and ions, Al neutrals and O neutral are formed. As the O2 background pressure increases from 3 Pa to 26 Pa, the energy of the plasma species are moderated. The results show that the ions density and velocity reduced significantly above 13 Pa. The velocity of the ions reduced from 14 kms−1 to 11 kms−1 at 13 Pa, while the ions energy reduced from 63 eV to 42 eV respectively. Below 13 Pa, crystalline and homogeneous AZO nanostructured films were formed. Above 13 Pa, the process results in low crystallinity films with higher porosity. The resistivity of the films also increases from 0.1 ohmcm to 24 ohmcm as the pressure increased. At fixed O2 background pressure of 3 Pa, the adatom mobility of atoms on the substrates is altered by substrate heating. The resistivity of the films decreased to 10–3 ohmcm when the substrates are heated to 100 °C–300 °C during deposition. The films with highest carrier density of 1020 cm−3 and carrier mobility of 13 cmV−1 s−1 are achieved at 200 °C.

The generation of a homogeneous plasma plume is necessary for the pulsed laser deposition of thin films. In this work, we investigate the effects of nanosecond-duration laser pulses to ablate polycrystalline Si targets in vacuum ( −4 Pa) at room temperature. The laser wavelength covers the range from ultra-violet to infrared by using a KrF (248 nm, 25 ns) and a Nd:YAG (1064 nm, 532 nm, 355 nm, 5 ns) laser. The films were deposited at laser fluences from 1 to 6 J/cm 2 and characterized by atomic force microscopy and spectroscopic ellipsometry. Time-integrated optical emission spectra were obtained for excited neutrals and ionized Si species in the plasma produced between 0.5 and 11 J/cm 2 . The relation between the ionized species and film properties were discussed.

ZnO based nanomaterials attract tremendous interest for applications in optoelectronics and sensors. Among the various chemical and physical deposition methods, laser produced plasma enable the deposition at relatively low or room temperature because of the capability to produce vapor/species with a wide range velocity and energy. The active plasma constituent may also be beneficial in promoting the formation of nucleation site for nanomaterials growth. In this work, a 355 nm and 532 nm laser is used for plasma plume generation from an Al-doped ZnO (AZO) target in different background gas while Si and glass substrates were held at room temperature to ensure that no external thermal energy was involved in materials growth. The presence of ambient gas condition during deposition affect the plasma generation and expansion mechanisms and can results in distinctly different growth mode. O2 background gas at optimized pressure preserved the stoichiometry of the final AZO films, while heavier or large gas molecules such as Ar effectively confined the plasma plume and increase probability of collisions. In addition, Ar gas may also enhance the generation of zinc suboxide species, which is important to the formation of ZnO nanostructure. The effects of different background gas on the self-assembled growth of AZO nanostructure in laser ablated plasma are discussed.

In this work, we investigated the laser ablation and deposition of Si and Ge at room temperature in vacuum by employing nanosecond lasers of 248 nm, 355 nm, 532 nm and 1064 nm. Time-integrated optical emission spectra were obtained for neutrals and ionized Ge and Si species in the plasma at laser fluences from 0.5 to 11 J/cm2. The deposited films were characterized by using Raman spectroscopy, scanning electron microscopy and atomic force microscopy. Amorphous Si and Ge films, micron-sized crystalline droplets and nano-sized particles were deposited. The results suggested that ionized species in the plasma promote the process of subsurface implantation for both Si and Ge films while large droplets were produced from the superheated and melted layer of the target. The dependence of the properties of the materials on laser wavelength and fluence were discussed.

This paper presents the results, analysis and discussions of parametric studies of diamond-like carbon (DLC) thin films by pulsed Nd:YAG laser deposition. Effects on the DLC properties and growth rate were investigated by varying the deposition parameters, namely the laser wavelength and fluence, substrate and temperature. For characterization, visible Raman spectroscopy, current-voltage measurement, optical interferometry, and optical absorption technique were employed. Comparisons were made with previous work by other workers who had also employed pulsed Nd:YAG lasers. The results also supported the subplantation mechanism for DLC formation.

Nickel (Ni) thin films were deposited on glass substrates in high vacuum and at room temperature with third-harmonic or 355-nm output from a nanosecond Nd:YAG laser. At low laser fluence of 1 J/cm2, the deposition rate was about 0.0016 nm/shot which increased linearly until 4 J/cm2. Above 4 J/cm2, the onset of phase explosion in the ablation abruptly increased the optical emission intensity from laser-produced Ni plume as well as thin-film deposition rate by about 6×. The phase explosion also shifted the size distribution and number density of Ni droplets on its thin-film surface. On the other hand, the surface structures of the ablated Ni targets were compared between the scan-mode and the fixed-mode ablations, which may suggest that droplets observed on the thin-film surface were caused by direct laser-induced splashing of molten Ni rather than vapour-to-cluster condensation during the plume propagation.

Al-doped ZnO (AZO) thin films were deposited on p-Si (100) by pulsed laser deposition at room temperature to form AZO/p-Si heterojunctions. Crystalline films with different properties were obtained. The heterojunctions exhibit diode behavior in dark and responded to illumination of broadband visible (400 nm ~ 750 nm) and/or ultraviolet (368 nm) light in applied voltage range of only ±1 V. Visible photons are mostly absorbed in p-Si and UV photons were absorbed in AZO layer. However, the defects level within the bandgap of the AZO layer would also contribute to photocurrent under visible light illumination. The best photodetection was obtained for AZO with resistivity of 1 Ωcm and low defects density where the sample response to either UV or visible light by changing the biasing voltage from −1 V or +1 V.

A thorough study of MSnO 3 (M=Ca, Sr and Ba) compounds with respect to their synthesis, processing and microstructural characterization has been made. In order to establish a standard methodology with identical and beneficial microstructure and reproducible electrical characteristics, a novel preparative method called self-heat-sustained (SHS) reaction technique was employed. Evolution of microstructure which is intimately related to the envisaged properties in the ceramics, was closely and systematically followed in terms of wide temperature-soak time ( T-t ) profiles. The results showed that while a well-densified microstructure with small grain size (∼1 μm) and near zero porosity could be obtained by selecting a sintering schedule of 1350°C/ x h (48 h x ⩽ 60 h) for CaSnO 3 samples, very well sintered samples with relatively larger grains (3–5 μm) and minimal porosity could also be obtained by sintering at 1600°C for 2 h. Well-densified microstructure with small grain size and zero or near zero porosity could be obtained by a sintering schedule of 1350°C/ x h (12 h x ⩽ 24 h) in SrSnO 3 samples. Sintering of BaSnO 3 proved to be the most difficult. The BaSnO 3 samples could only be densified to the desired level by soaking the powder compacts for 2 h at 1600°C. The “sugar cube” features were replaced by the spherical grains (average size 1–2 μm).

Effects of O 2 , N 2 , Ar and He on the formation of micro- and nanostructured indium tin oxide (ITO) thin films were investigated in pulsed Nd:YAG laser deposition on glass substrate. For O 2 and Ar, ITO resistivity of ≤ 4 × 10 -4 Ωcm and optical transmittance of > 90% were obtained with substrate temperature of 250 °C. For N 2 and He, low ITO resisitivity could be obtained but with poor optical transmittance. SEM images show nano-structured ITO thin films for all gases, where dense, larger and highly oriented, microcrystalline structures were obtained for deposition in O 2 and He, as revealed from the XRD lines. EDX results indicated the inclusion of Ar and N 2 at the expense of reduced tin (Sn) content. When the ITO films were applied for fabrication of organic light emitting devices (OLED), only those deposited in Ar and O 2 produced comparable performance to single-layer OLED fabricated on the commercial ITO.

Nanowires of indium tin oxide (ITO) were grown on catalyst-free amorphous glass substrates at relatively low temperature of 250 °C in argon and helium ambient by the Nd:YAG pulsed laser deposition technique. All the ITO samples showed crystalline structure due to substrate heating and the (400) X-ray diffraction peak became relatively stronger as the pressure was increased. The surface morphology was also changed from compact, polycrystalline thin-film layers to a dendritic layer consisting of nanowires for some limited pressure ranges. The transition from the normal thin-film structure to nanowires was likely due to the vapor–liquid–solid mechanism but under catalyst-free condition. These nanowires tended to grow perpendicularly on the glass substrate, as observed with the transmission electron microscopy (TEM), which also confirmed that these nanowires were crystalline.

Al-doped ZnO (AZO) films were deposited on glass and polycarbonate (PC) at room temperature by using pulsed Nd:YAG laser at 355 nm. AZO thin films were obtained for both substrates at laser fluences from 2 to 5 J/cm2 in O2 partial pressure of 2.1 Pa. The effects of laser fluence on the structural, electrical, and optical properties of the films were investigated. The films with lowest resistivity and highest transmittance have been obtained at 2 J/cm2. The resistivities were 2.29×10−3 Ω cm for AZO on glass and 1.49×10−3 Ω cm for AZO on PC. With increasing laser fluence, the deposited films have lower crystallinity, higher resistivity, and smaller optical bandgap.

Low-temperature growth of indium tin oxide (ITO) nanowires (NWs) was obtained on catalyst-free amorphous glass substrates at 250??C by Nd:YAG pulsed-laser deposition. These ITO NWs have branching morphology as grown in Ar ambient. As suggested by scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM), our ITO NWs have the tendency to grow vertically outward from the substrate surface, with the (400) plane parallel to the longitudinal axis of the nanowires. These NWs are low in electrical resistivity (1.6???10?4???cm) and high in visible transmittance (?90?96%), and were tested as the electrode for organic light emitting devices (OLEDs). An enhanced current density of ?30?mA?cm?2 was detected at bias voltages of ?19?21?V with uniform and bright emission. We found that the Hall mobility of these NWs is 2.2?2.7 times higher than that of ITO film, which can be explained by the reduction of Coulomb scattering loss. These results suggested that ITO nanowires are promising for applications in optoelectronic devices including OLED, touch screen displays, and photovoltaic solar cells.