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Organic solar cells based on Poly (3-hexylthiophene) [6,6]-phenyl C61-butyric acid methyl ester (P3HT-PCBM) were fabricated in standard architecture by spin-coating on glass and on flexible polyethylene terephthalate (PET) substrates in ambient laboratory environment. In addition to the conventional DC characterization, impedance spectroscopy was used in order to study the capacitive behavior of the devices and obtain their electrical parameters. In combination with the electrical characterization methods, laser-beam-induced current (LBIC) measurements were used as a non-destructive method of mapping the photocurrent distribution and analyzing local device failures and macroscopic defects (shunts, dark spots, defects). The results of the study can be used to develop guidelines for the development and design of P3HT:PCBM solar cells in ambient environment.

Transparent conductive electrodes (TCO) serve as window and contact layers and they should combine high optical transmittance with low electrical resistivity. Recently ZnO has been considered to be the most promising TCO material in view of cost and properties. Chalcopyrite based solar cells commonly consist of Cu(In,Ga)Se2 (CIGS) absorber layer and a sputter sequence of undoped and doped ZnO layers in a structure: glass/Mo/CIGS/CdS/ZnO/ZnO:Al. In some cases, ZnO plays the role of the buffer layer itself as an alternative of the mostly used toxic CdS. An advanced application of this material is considered to be involving in Organic Solar Cells (OSCs) as Electron Transporting Material (ETM). The work presents fabrication of uniform resistive thin (50-100 nm) undoped ZnO films serving as buffer layers and conductive Al-doped ZnO films (Al:ZnO) with thickness in the range of 100-500 nm. In the latter case the film thickness was optimized to combine high transmittance and low resistivity. Both types of films are with good adhesion and possess a transmittance over 90% in the visible region. Highly transparent bi-layer films (ZnO/ZnO:Al) were finally embedded in the solar cell structure: glass/Mo/CIGS/ZnO/ZnO:Al/Al.

A solution deposition technique is investigated as an approach for formation of nanostructured ZnO films with tailored geometric shape and aspect ratio, electrical conductivity, and high optical transmittance. Having in mind thermodynamic particulars of ZnO precipitation from aqueous solutions, we show deposition of thin films of intrinsic ZnO with well-defined hexagonal wurtzite structure and with high optical transmittion in the visible region. Deposition of doped layers of Al:ZnO with aluminium concentration up to 3 wt% does not cause degradation of the wurtzite structure and sheet resistance of the films is near 8.0*102 Ω / □. After applying thermal annealing, the absorption edge gets sharper and optical band gap is found to be near 3.26 eV for direct transitions. Addition of the ethanol in the aqueous deposition solution leads to formation of ZnO nanostructured films with trigonal configuration.

ZnO has been widely used as electron selective material in P3HT:PCBM organic solar cells with either conventional or inverted architecture in order to enhance the extraction of electrons and block the collection of holes at one electrode. In this work we investigate the influence of ZnO nanoparticles electron transport layer (ETL) on the performance and stability of P3HT:PCBM based organic solar cells with conventional architecture and magnetron sputtered back Ag contacts. Their stability in the dark and under real outdoor conditions was monitored by current-voltage measurements and impedance spectroscopy. The impedance spectra were taken as a function of applied bias under illumination in order to reveal more information about the degradation mechanisms taking place in the device.

In the present study, thermally evaporated thin copper (I) bromide films were investigated as a potential hole-transport material for hybrid perovskite solar cells in a standard configuration. The films were deposited on top of glass substrates; the measured transparency was 80 %. The structural and morphological analyses revealed a dense polycrystalline structure of γ-CuBr. The analysis of the surface chemical composition demonstrated that copper was in a Cu1+ state and the films were stoichiometric. Electrical measurements were performed with deposited planar silver or copper electrodes. The layers were highly resistive; however, a current increasing with the time was observed when the samples were biased by a dc voltage of 20 V for two hours, which we speculate might be due to a possible new conduction mechanism.

In this paper, TiO2/Ag/TiO2 multilayers, deposited by magnetron sputtering technique at room temperature are used as transparent conductive layers for Liquid Crystal (LC) devices fabrication. The measured electro-optical modulation characteristics and phase retardation of LC cell based on TiO2/Ag/TiO2 electrode show improved electro-optic performances in comparison with LC reference cell using commercial Indium Tin Oxide (ITO). Low sheet resistance and high transparency of TiO2/Ag/TiO2 multilayers open a great potential for next generation ITO-free liquid crystals electro-optical modulators.

High effective selective absorbing bimetallic structures of Sn and Ni for solar thermal collectors have been investigated. They were produced by cathode electrodeposition on polished copper plates from water solution. Scanning electron microscopy micrographs show that they consist of a highly branching layer of bimetallic needles. They serve as a radiation trap for the solar radiation because of multiple reflections. The reflectance spectra were measured in the visible and infrared range. The absorptance of the coating was calculated as 98% in the solar radiation range and the thermal emittance in the infrared region at 100 °C - as 10%. The selective absorbing coatings are investigated by X-ray diffraction analysis and X-ray photoеlectron spectroscopy as well as optical spectra in the UV-VIS and IR region. The samples with selective absorbing coatings have been tested at natural solar radiation. The results show that the new coatings have substantial advantages in comparison to the widely used black chrome.

Transparent and conductive oxide/ metal/ oxide nanolaminate structures were deposited on glass and polymer substrate by RF magnetron sputtering without substrate heating. The Ag nanoparticles with different size and distance between neighboring particles were located on the interface of two thin oxide layers. This sputtering configuration allows obtaining thin films with homogeneous thickness. The three targets give the opportunity to deposit successively three different layers without opening the chamber. The developed process for transparent conducting coating is a low temperature and it is suitable for application on organic materials as substrate and foils. The experiment with different substrates manifest that the optical transparency of the conducting coating depends on substrate material. The obtained results have demonstrated that the nanolaminate structures oxide/metal/oxide (OMO) as TCO coating are especially suitable for applications in flexible electronics and optoelectronics

Thin films of molybdenum oxide were deposited by radio frequency (RF) magnetron sputtering in Ar from a MoO3 target at different deposition power on glass and silicon substrates. The thickness of the films was determined by profilometer measurements and by ellipsometry. The films were annealed in air at temperatures between 200 and 400°C in air. The optical transmission and reflection spectra were measured. The conductivity of the as deposited and annealed films was determined. The crystal structure was probed by Raman spectroscopy. The oxidation state of the surface was studied by X-ray photoelectron spectroscopy (XPS) spectroscopy. The deposition technique described above was used to experiment with MoOx as a hole transport layer (HTL) in polymer solar cells with bulk hetrojunction active layer, deposited by spin coating. The performance of these layers was compared with poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS), which is the standard material used in this role. The measured current-voltage characteristics of solar cells with the structure glass/ITO/HTL/Poly(3-hexyl)thiophene (P3HT):[6,6]-phenyl-C61- butyric acid methyl ester (PCBM)/Al demonstrate that the studied MoOx layer is a good HTL and leads to comparable characteristics to those with PEDOT:PSS. On the other hand the deposition by magnetron sputtering guarantees reliable and repeatable HTLs.

The aim of this study was formation of a multilayered transparent conductive nanolaminate structure with optimized conductivity vs. transparency parameters. The nanolayered structure comprised one or two thin layers of dielectric materials. The overall electrical conductivity was modified by tuning the size of the planar metal granules. Magnetron sputtering system with three different targets was used for layers deposition. The advantages are: the good reproducibility of a low-temperature process allows for effective process control and, optionally, selective formation of conductive areas in a dielectric structure. Our studies revealed that the relation between the sheet resistance and the maximum transparency in the visible spectral range depends on the size of the metal granules and the film thickness of the dielectric coating. The technology provides transparent conductive coatings with well-controlled optical and electrical properties.

We present a detailed investigation of the properties of silicon dioxide deposited at a low temperature. The advantages of this process include its low thermal requirements (about 200 °C), the absence of corrosive by-products and the lack of need of vacuum equipment. Sol solutions were prepared for the deposition of ultrathin SiO2 films by spin-coating at the low annealing temperature of 200 °C. The layers' thickness was 24 nm and 5 nm. We describe in detail the material properties of this novel low-temperature SiO2 layers obtained by extensive characterization using Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM), XPS spectroscopy, capacitance-voltage (C-V) and current-voltage (I-V) measurements. The ultrathin oxide layers on Si substrates show good dielectric properties.

A double-layer structure of Al2O3 over ZrO2 film is studied. Minimization of the average weighted reflectance is carried out to optimize the thickness of the two layers in the antireflection coating. An optimal value of 2.17% for the weighted average reflection is estimated. The optimal thicknesses of the layers are 49 nm for the bottom and 45 nm for the top layer. Low temperature spin coating technique is used to deposit ZrO2 and Al2O3 films from sol gel solutions on polished silicon wafers, GaAs multilayer heterostructures and AlGaAs/GaAs solar cells. The density of the short-circuit photocurrent increases from 25 mA.cm−2 for solar cells without an antireflection coating to 36 mA.cm−2 for those with a double layer coating.