Metal salt modified PEDOT : PSS as anode buffer layer and its effect on power conversion efficiency of organic solar cells

The effects of metal chlorides such as LiCl, NaCl, CdCl2 and CuCl2 on optical transmittance, electrical conductivity as well as morphology of PEDOT:PSS films have been investigated. Transmittance spectra of spun PEDOT:PSS layers were improved by more than 6 to a maximum of 94 in LiCl doped PEDOT:PSS film. The surface of the PEDOT:PSS films has exhibited higher roughness associated with an increase in the electrical conductivity after doping with metal salts. The improvement in the physical properties of PEDOT:PSS as the hole transport layer proved to be key factors towards enhancing the P3HT:PCBM bulk heterojunction (BHJ) solar cells. These improvements include significantly improved power conversion efficiency with values as high as 6.82 associated with high fill factor (61) and larger short circuit current density (�18 mA cm-2). Keywords: Chlorine compounds; Conversion efficiency; Electric conductivity; Electrodes; Heterojunctions; Metals; Semiconductor doping; Solar cells, Electrode modification; Metal salt; Organic solar cell; P3HT:PCBM; PEDOT:PSS, Conducting polymer

Electrodeposition of CdS thin-films from cadmium acetate and ammonium thiosulphate precursors

Cadmium sulphide (CdS) thin-films have been electrodeposited using two electrode system to be used as the hole back diffusion barrier (hbdb) layer for graded bandgap solar cells with p-type windows. Cadmium acetate dihydrate [Cd(CH3COO)2·2H2O] and ammonium thiosulphate [(NH4)2S2O3] have been used as the cadmium (Cd) and sulphur (S) precursors respectively. In this work, CdS layers have been grown on glass/FTO (fluorine doped tin oxide) substrates at cathodic potentials ranging from 1300 to 1460 mV in order to find the best growth voltage. N-type conductivity is observed for all the layers and band-gap ranged between ~ 2.36 and ~ 2.40 eV for as-deposited layers and ~ 2.31 and ~ 2.36 eV for air-annealed layers. X-ray diffraction (XRD) analysis revealed cubic/hexagonal mixed crystallinity for the as-grown layers which indicates a tendency of transiting towards hexagonal structure upon annealing. Compositional and morphological characteristics of the layers have been investigated with energy dispersive X-ray (EDX) and scanning electron microscopy (SEM) respectively

Excimer laser processing of inkjet-printed and sputter-deposited transparent conducting SnO2:Sb for flexible electronics

The feasibility of low-temperature fabrication of transparent electrode elements from thin films of antimony-doped tin oxide (SnO2:Sb, ATO) has been investigated via inkjet printing, rf magnetron sputtering and post-deposition excimer laser processing. Laser processing of thin films on both glass and plastic substrates was performed using a Lambda Physik 305i excimer laser, with fluences in the range 20–100 mJ cm− 2 reducing sheet resistance from as-deposited values by up to 3 orders of magnitude. This is consistent with TEM analysis of the films that shows a densification of the upper 200 nm of laser-processed regions

What are the Prospects of 3D Profiling Systems Applied to Firearms and Toolmark Identification?

This paper details a comparative pilot study of 3D (three dimensional) imaging technologies for potential application in forensic firearms and toolmark identification; as such it reviews the most up-to-date profiling systems. In particular, the paper focuses on the application of 3D imaging and recording technology as applied to firearm identification, being a specialised field within the discipline of toolmark identification. Each technology under test employs a different technique or scientific principle to capture topographic data i.e. focus-variation microscopy, confocal microscopy, point laser profilometry and vertical scanning interferometry. To qualitatively establish the capabilities and limitations of each technology investigated, standard reference samples were used and a set of specific operational criteria devised for successful application in this field. The reference standard crucially included and centred on was the National Institute of Standards and Technology (NIST) 'standard bullet'. This was to ensure that evaluation represented the practical examination of ballistic samples i.e. fired cartridge cases and bullets. It is concluded that focus-variation microscopy has potentially the most promising approach for a forensic laboratory instrument, in terms of functionality and 3D imaging performance, and is worthy of further investigation

Temperature dependent characteristics of La2O2S: Ln [Ln = Eu,Tb] with various Ln concentrations over 5-60 ºC

This research is aimed at developing an optical sensor for remotely measuring human skin temperature in electromagnetically hostile environments, such as within a magnetic resonance imaging (MRI) scanner. In this feasibility study, various concentrations of europium doped lanthanum oxysulphide (La2O2S: Eu- 0.1-15 mol % (m/o)) and terbium doped lanthanum oxysulphide (La2O2S: Tb - 0.005-50 m/o) have been investigated in terms of crystallinity, photoluminescent (PL) spectral and decay time characteristics. For both phosphors, X-ray diffraction (XRD) has shown that as dopancy increases, the (100) and (002) reflections merge and there is a reduction in the c-axis parameter as well as the crystallite size. Photoluminescent characterisation (337 nm excitation) has also shown a dependency to dopant concentration through variance of peak intensity. Temperature dependent decay time measurements were carried out over a low temperature range of 5 to 60 °C. Optimum brightness of these temperature dependent lines is achieved at concentrations of 1 and 10 m/o for La2O2S: Eu and La2O2S: Tb respectively. However, optimum temperature dependency is achieved at lower concentration for La2O2S: Eu, specifically at 0.1 m/o. In comparison to conventional phosphor temperature dependent characteristic, La2O2S: Tb showed an increase in decay time with respect to temperature for concentrations above 2 m/o

Photo-engineered optoelectronic properties of indium tin oxide via reactive laser annealing

Abstract: Transparent conductive oxides are appealing materials for optoelectronic and plasmonic applications as, amongst other advantages, their properties can be modulated by engineering their defects. Optimisation of this adjustment is, however, a complex design problem. This work examined the modification of the carrier transport properties of sputtered tin-doped indium oxide (ITO) via laser annealing in reactive environments. We relate the optical modifications to the structural, compositional, and electronic properties to elucidate the precise mechanisms behind the reactive laser annealing (ReLA) process. For sufficiently high laser fluence, we reveal an ambient-dependent and purely compositional modulation of the carrier concentration of ITO thin films. Hereby, we demonstrate that ReLA utilises the precise energy delivery of photonic processing to enhance the carrier mobility and finely tune the carrier concentration without significantly affecting the crystal structure. Exploitation of this phenomena may enable one to selectively engineer the optoelectronic properties of ITO, promising an alternative to the exploration of new materials for optoelectronic and photonic applications

Organic solar cells: study of combined effects of active layer nanostructure and electron and hole transport layers

An organic solar cell based on Poly (3-hexathiophine-2,5-diyl) and [6,6]-Phenyl C61 butyric acid methyl ester has been subjected to all layers treatment and was investigated for combined effects of the these layers on device performance. These treatment included optimization of active layer morphology and thickness and improving the structure of the hole and electron transport layers, as well as subjecting the full device to optimum post deposition thermal treatment. Such a device has shown an increase in the optical absorption intensity in the near infrared region compared to the reference device, which is thought to be advantageous for producing high current density. The increase in the current density has also been correlated with light trapping within the active layer and the possibility of the occurrence of total internal reflection, which was explained using total internal reflection spectroscopic ellipsometry measurements. The current density-voltage characteristics have been measured in dark and under illumination. Power conversion efficiency as high as 7% has been achieved correlated with a fill factor of 71%

Handbook of Visual Display Technology

The Handbook of Visual Display Technology is a unique work offering a comprehensive description of the science, technology, economic and human interface factors associated with the displays industry. An invaluable compilation of information, the Handbook will serve as a single reference source with expert contributions from over 150 international display professionals and academic researchers. All classes of display device are covered including LCDs, reflective displays, flexible solutions and emissive devices such as OLEDs and plasma displays, with discussion of established principles, emergent technologies, and particular areas of application. The wide-ranging content also encompasses the fundamental science of light and vision, image manipulation, core materials and processing techniques, display driving and metrology