A metal-polymer nanocomposite of platinum–polyaniline (Pt/PANI) was deposited on fluorine-doped tin oxide glass substrates to function as a counter electrode for polysulfide redox reactions in cadmium sulfide quantum dot-sensitized solar cells. In addition, front-side illuminated photoelectrodes were sensitized by silver (Ag) nanoparticles (NPs) as an interfacial layer between a transparent conducting oxide substrate and a TiO2 layer. This configuration, i.e., both the Pt/PANI counter electrode and the Ag NPs in the photoanode, leads to 1.92% in the power-conversion efficiency (PCE) of the fabricated cells. A PCE enhancement of around 21% was obtained for the Ag NPs-sensitized photoanodes, as compared with the Ag NPs-free one. The improved performance can be attributed to the easier transport of excited electrons and the inhibition of charge recombination due to the application of an Ag NPs layer. Electrochemical impedance spectroscopy measurements showed that once Ag NPs are incorporated in a photoanode, electron transport time decreases in the photoanode structure.
Interconnecting layers (ICL) play an important role in regulating the performance of tandem devices. We report the design of a solution-processed ICL that consists of a silver/polymer nanocomposite deposited on the top of a TiO2 layer. This nanocomposite contains modified poly (3,4-ethylenedioxythiophene) polystyrene sulfonic acid (PEDOT:PSS), and silver nanoparticles (Ag NPs) synthesized by the chemical reduction of silver nitrate in the presence of PEDOT:PSS. Formation of Ag NPs was confirmed by monitoring the plasmon absorption peak characteristics in the UV–visible spectrum of the synthesized nanocomposite. Transmission electron microscopy analysis indicated the presence of spherical silver NPs in a polymer matrix with a mean size of around 20 nm. The sheet resistance of PEDOT:PSS was found to be 2474±35 Ω/sq. It was changed to 445±28 Ω/sq after solvent modification and decreased to 53.31±3.59 Ω/sq after synthesizing silver NPs in the polymer medium. Meanwhile, the transparency of the nanocomposite film deposited on TiO2 was 89.6%, which is considered appropriate for an interconnecting electrode. We demonstrated that by incorporating a silver/polymer nanocomposite as a hole-transporting layer in contact with TiO2 as an electron-transporting layer, the ohmic behavior of ICL is enhanced with respect to pristine PEDOT:PSS. P3HT:PCBM-based tandem solar cells based on this solution-processed intermediate electrode represent significantly increased open-circuit voltage (Voc), reaching close to the sum of the single cells. By incorporating the nanocomposite in the tandem structure, a Voc of 1.1 V was obtained. This value was almost the sum of the Voc of two single cells, which was 1.18 V.
Silver (Ag) nanoparticles (NPs) were synthesized and used as an interfacial layer in the photoanode of quantum dot sensitized solar cells (QDSSCs). Two different methods were employed to determine the size and shape of the Ag NPs. Using transmission electron microscopy images and calculations based on Mie theory, a size of 5 nm and a spherical shape were obtained for the sensitized Ag NPs. Then these NPs were applied in a fluorine-doped tin oxide (FTO)/Ag/TiO2/CdS photoanode structure in the QDSSCs. As an interfacial layer, Ag NPs were dip-coated on FTO between an FTO glass and a TiO2 layer. A successive ionic layer adsorption and reaction method was used for deposition of CdS quantum dots on the TiO2 films. A power conversion efficiency of ∼1.45% was obtained for FTO/Ag/TiO2/CdS cells, which was ∼40% higher than ∼1.05% found for noninterfacial layer FTO/TiO2/CdS cells. The easier transport of excited electrons and the inhibition of charge recombination due to the application of an Ag NPs layer are concluded to be responsible for the improved performance of the cells and their increased photocurrent.
Using the grazing incidence pumping technique with a 600 mJ, 500 ps background pulse and a 250 mJ, 200 fs main
pulse the lasing emission from a molybdenum target has been studied. A flat field spectrometer designed to observe the
X-ray laser emission in both the first and second orders was used to record the time integrated data. Time resolved data
was obtained by installing an Axis-Photonique PX1 X-ray streak camera to observe the first order output from the
spectrometer whilst retaining the time integrated second order observation. In this paper both time integrated and time
resolved data are presented for a range of grazing angles, target lengths, delays between pumping pulses and pumping
energy. Comparisons are also drawn with simulations from the Ehybrid and Medusa codes. An additional experiment is
also described in which a two colour pumping method is used to investigate lasing at short wavelength from high Z
targets (Z ≥ 62).
The construction of a surface corona UV pre-ionized TEA CO2 laser is described and dependence of its average output energy of the laser to gas mixture, discharge voltage and repetition rate is investigated. The electric circuit diagram and geometry of the pre-ionization system are presented. Configuration of circuit has been designed to produce only impulsive voltage difference between the laser electrodes. Also, the triggering configuration of trigatron is prepared for fast operation to minimize the arc occurrence as much as possible. Some data of current, voltage, laser pulses and average output energy versus gas mixture and applied voltages are given. IR spectrometer is used for measurements of central output wavelength of the laser. Operation of the laser on two adjacent vibrational-rotational transitions of CO2 molecule has been observed that shows the ability of this laser for working on multi-line in a same time for special applications.
A number of laser transitions in the region of 12-13 μm have been obtained by optical pumping of NH3 molecule using a tunable TEA CO2 laser. By studying several different experimental arrangements, it is shown that the optimum pure NH3 gas pressure at room temperature is about 5 mbar. Moreover, some buffer gasses such as N2, H2 and He were employed and it was found that He is the most efficient gas for which the maximum efficiency up to 8% with the mixture of NH3: He =7:16 was obtained. In this condition, the maximum energy per pulse of 125 mJ was achieved. The tunable operation of this laser was established in two distinct wavelengths of 12.812 μm and 12.08 μm.
A single longitudinally excited CW CO2 laser, designed based on gas flow mechanism has been used for small signal gain measurements. By inserting a ZnSe stack polarizer set at Brewster angle inside the laser cavity the absorption loss at the critical condition was obtained. The small-signal gain measurements were performed under various laser operational conditions such as gas pressure and input electric power. At the same experimental conditions, the values of the saturation intensity were calculated from the output power and the measured small-signal gain values. The results are compared with those reported previously by other researchers.
By coupling a CW C02 and a TEA CO2 laser through a grating simultaneously used for both resonators, without any additional optical elements, the CW laser radiation was injected without loss into the TEA CO2 laser optical cavity. Thus, longitudinal and transverse single mode operation of the TEA CO2 laser was achieved successfully without any intracavity limiting apertures an evident by the smooth shape of detected pulses. Furthermore, a 3x3 cm cross section single mode beam with unaffected energy of about 4 J/pulse was obtained. This specially designed array due to its observed spectral coincidence of CW radiation and pulsed emission indicates exact alignment of injected CW radiation with the optical axis of TEA CO2 laser resonator without significant angular deviation. Slight radial deviation, however, did not have any detectable destructive effect on the single mode output signals. This compact and simple structure single mode TEA CO2 laser with its stability and simple adjustability can be very useful particularly for portable units such as atmospheric lidar instruments.
Operation of a TEA CO2 laser with parallel spark array pre-ionization is investigated. Low repetition rate pulsed laser has been made having integrated pre-ionization and peaking circuits. The effect of gas mixture, applied voltage and capacity of the main, peaking and preionization capacitors on output power of the laser are presented. Total efficiency up to 7% was obtained and although the fraction of the He in gas mixture was only 58% stability of discharge was good (2 arc in 55 discharges).
Low pump energy transient gain x-ray lasers in Ti at 32.6 nm, 30.15 nm, in V at 30.4 nm and Ge at 19.6 nm using picosecond pulse heating of a long pulse preformed plasma of neonlike ions has been realized for the first time. Gain saturation was demonstrated in Ti and Ge XRL. Results of pump consumption, x- ray divergence and output energy are given.
The use of multi-pulse irradiation of neon-like ions has been shown to produce orders-of-magnitude enhancement of x-ray laser output. Recent results obtained at the Rutherford Appleton Laboratory are reviewed with an emphasis on understanding the reasons for the enhancement. Simulations with the fluid and atomic physics code EHYBRID are used to show that enhancement occurs because of a spatial enlargement of the gain region and consequent better propagation of the x- ray laser beam along the gain region.
Current successful approaches for achieving soft x-ray lasing typically require pumping laser pulses of duration approximately ns and energy approximately kJ (collisionally pumped schemes) or approximately ps pulses and powers of approximately several TW (recombination-pumped schemes). For applications, it is important to improve the efficiency of soft x-ray lasers and so reduce the required power of pumping lasers. The effect of pre- pulse on neon-like collisionally pumped lasers has been investigated using the LULI laser (Ecole Polytechnique, France). A small pre-pulse level approximately 10-3 of the main pulse energy was found to increase the J equals 0 minus 1 neon-like zinc laser output at 21 nm by an order-of-magnitude with a comparable increase in efficiency. A double pumping laser pulse on neon-like yttrium lasing output at 15 nm obtained with the VULCAN laser (Rutherford Appleton Laboratory, England) was also found to increase the x-ray lasing efficiency. With adiabatically cooled recombination lasing, it is shown that approximately 2 ps pulses are optimum for achieving the desired ionization balance for lasing output. The possibility of achieving recombination lasing at short wavelengths on lithium-like ions with longer pulse lasers has been investigated using the ASTERIX laser (Max-Planck Quantenoptik, Germany). These results are presented and interpreted to provide possible directions for improving the efficiency of x-ray lasers.
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