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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.

We studied the degradation of different types of bulk heterojunction devices, in which the materials comprising the active layer and/or the materials used for the back electrode are varied. The devices are deposited on ITO covered glass and have the structure PEDOT:PSS/BHJ/Me, where PEDOT:PSS is the hole transport layer, BHJ (bulk heterojunction) is the active layer comprising a polymer donor (e.g. PTB7, PCDTBT) and a fullerene derivative acceptor (e.g. PC60BM, PC70BM) deposited by spin coating, Me is the metal back contact, which is either Ag or Al deposited by magnetron sputtering or thermal evaporation. The device performance was monitored after storage in the dark at ambient conditions by following the evolution of the J-V curve over time. Results of real conditions outdoor degradation studies are also presented. The stability of the different solar cell structures studied is compared.

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.

A solution based deposition method to form nano-sized thin films of molybdenum oxide suitable for photovoltaic device applications is presented. The samples were deposited by spin-coating from molybdenum metal organic precursor solution on soda lime glass substrates. The influence of the process parameters such as spinning regime and concentration of the precursor solutions on the thickness and morphology of the films were investigated. The thermal decomposition of the molybdenum precursor and oxide formation were investigated by differential scanning calorimetry and characteristic patterns showed transitions up to 300oC followed by a zone of stability. Optical spectroscopy measurements in the wavelength range from 300 to 1800 nm presented an increase in transparency when temperature of annealing was raised up to 400oC. Raman scattering analysis revealed the presence of mixed molybdenum oxides. Measurements of the electrical conductivity were performed by the 4-point method.

Two types of polymer solar cells with active layers of P3HT:PCBM and PCDTBT:PCBM in a standard configuration were deposited by spin-coating the polymer layers and sputtering the Ag back contacts. After encapsulation, they were subjected to post-deposition annealing and were studied by measuring their current-voltage characteristics and quantum efficiency spectra. Their stability was examined by exposing them to solar radiation in open-circuit conditions for several hours every day for a total of 80 hours. Their characteristics were measured regularly throughout this period. The performance of the two types of cells are compared and discussed.

Thin films of tin sulfide (SnS) were prepared by thermal evaporation technique on glass substrates and on n-type Si substrate and their physical properties were studied. The phase of the obtained thin films before and after thermal treatment was confirmed by X-ray diffraction analysis and Raman spectra. Optical transmission and reflection spectra were measured in the wavelength range 300-1800 nm, and the data were used to determine the direct and indirect optical band gaps. Four-point measurements have revealed that SnS thin film exhibits p-type conduction. Current-voltage characteristics of the SnS/ n-Si structures demonstrate strong photosensitivity and photovoltaic effect. However, in order to be able to evaluate the potential applicability of this heterojunction for photovoltaic or electronic devices, further study and technological optimization has to be conducted.

The performance of bulk heterojunction P3HT :PCBM polymer solar cells is studied using current-voltage and spectral sensitivity measurements. Front transparent contacts of either ITO or a sputtered multilayer TiO2/Ag/TiO2 transparent conductive electrode are applied. Thin PEDOT:PSS and P3HT:PCBM polymer layers are deposited on these substrates by spin coating. The degradation of the solar cells is studied by subjecting them to UV irradiation. The obtained spectral sensitivity curves are analyzed in comparison with the optical absorption spectra of the transparent electrodes and active layers employed. It is observed that there is a pronounced dependence of the spectral sensitivity curves on the thermal treatment and UV irradiation applied to the solar cells. The performance of the multilayer TiO2/Ag/TiO2 transparent conductive electrodes is also studied in comparison with that of the ITO ones.

TiO2 films were prepared by a sol-gel technique with commercial TiO2 powder as a source material (P25 Degussa AG). After a special treatment, printing paste was prepared. The TiO2 layers were formed by means of drop-coating on Si-control wafers and on the Au-electrodes of quartz resonators. The surface morphology of the films was examined by scanning electron microscopy (SEM). Their structure was studied by Raman spectroscopy and the surface composition was determined by X-ray photoelectron spectroscopy (XPS). The layers had a grain-like surface morphology and consisted mainly of anatase TiO2 phase. The sensitivity of the TiO2 films to NO2 was assessed by the quartz crystal microbalance (QCM) technique. To this end, the films were deposited on both sides of a 16-MHz QCM. The sensing characteristic of the TiO2-QCM structure was investigated by measuring the resonant frequency shift (ΔF) of the QCM due to the mass loading caused by NO2 adsorption. The Sauerbrey equation was applied to establish the correlation between the QCM frequency changes measured after exposure to different NO2 concentrations and the mass-loading of the QCM. The experiments were carried out in a dynamic mode on a special laboratory setup with complete control of the process parameters. The TiO2 films were tested in the NO2 concentration interval from 10 ppm to 5000 ppm. It was found that a TiO2 loading of the QCM by 5.76 kHz corresponded to a system sensitive to NO2 concentrations above 250 ppm. On the basis of the frequency-time characteristics (FTCs) measured, AF at different NO2 concentrations was defined, the adsorption/desorption cycles were studied and the response and recovery times were estimated. The results obtained show that the process is reversible in the NO2 interval investigated. The results further suggested that TiO2 films prepared by a sol-gel method on a QCM can be used as a sensor element for NO2 detection.

A new combination of layers functioning as a transparent contact is proposed and tested in real solar cells. The contacts consist of TiO2 layers and thin metal layers (Ag, Cu) and are deposited by magnetron sputtering. The optical transmission and electrical conductivity of the transparent contact layers (TCL) are measured. The TCLs are applied as back contacts in bulk heterojunction polymer solar cells deposited on ITO covered glass and consisting of the following layers: ITO/PEDOT:PSS/P3HT:PCBM/back contact. The organic layers are deposited by spin-coating. For comparison, the same bulk heterojunction polymer solar cells are prepared with a sputtered Ag back contact. The first results show a dependence of the current-voltage parameters of the studied solar cells on the thickness of the different component layers of the transparent back contacts. There is a balance that has to be observed between the electrical characteristics of the contacts and their optical transparency. Future plans involve their inclusion as intermediate contacts in tandem organic solar cells.

Bulk-heterojunction solar cells based on P3HT:PCBM with Al or Ag electrodes deposited either by magnetron sputtering or by thermal evaporation were produced and their performance compared. The best results were obtained with thermally evaporated Al electrodes. Post-production annealing was applied to the already encapsulated samples and significantly enhanced the efficiency of all four types of cells. For both Ag and Al electrodes deposited by thermal evaporation post-annealing improved the I–V characteristics eliminating the S-shape usually typical for as deposited samples.

Results are presented on the deposition and characterization of thin SiO2 and Al2O3 films containing Tb3+ ions developed for application as spectral converters. The films are prepared by RF magnetron co-sputtering. The photoluminescence (PL) is measured at room temperature using the 488 nm line of an Ar laser. The dependence is studied of the PL intensity on the Tb concentration in the film. It is found that the intensity exhibits a maximum at about 1 at.%. Annealing studies are performed on SiO2:Tb using two different methods to improve the PL intensity. In both regimes of annealing, the best results are obtained at 650 − 700°C. After treatment at this temperature the Tb PL increases 2.5 − 3 times.

This article reports the synthesis of wire structured ZnO by electrochemical deposition on a glass substrate covered by thin film of ITO or SnO2 doped with F (SnO2:F) and on a carbon tissue. The influence of the structure of the transparent conductive films on the structural properties of the ZnO films obtained was studied by SEM and Raman spectroscopy. The results show that the films have a columnar structure with grain size of about 200-500 nm. The films deposited on the SnO2:F coated glass substrate have better structural properties. Pillar structure is observed on the surface of the fiber of the carbon tissue.