When small organic molecules (e.g. amino acids, nucleotides, and so on) are incorporated in metal oxide particles formed from metal alkoxide in the sol-gel process, the organic moieties can be removed readily by solvent washing or by degradative oxidation. Under proper conditions, nano-sized cavities corresponding to the shape of the individual organic moiety are produced within the metal oxide network as molecularly imprinted material such as surface molecularly imprinted TiO2. We tried to fabricate nano-sized particle of TiO2 to increase the effective contact area for the reactants, and further additional function for molecular recognition was intended to introduce through the surface modification of the molecular imprinting method in order to enhance the photoreduction of viologen. In this context, we prepared viologen imprinted TiO2 as an active and stable photocatalyst for photoreduction of viologen as a well-defined and readily identifiable and reversible electron carrier with appropriate redox potential for photoactivated TiO2. The basic concept of molecularly imprinting in this system is as follows. Oxidized viologen is generally twisted and dication molecule. While, reduced viologen is planar and monocation radical. Once TiO2 has such recognition site on its surface, it would be distinguishable through shape or charge recognition or both factors and facilitate the inclusion or exclusion of the target molecule result the enhancement of the reduction. After the preparation of the template, sol-gel imprinting was performed. Measuring its dynamic light scattering monitored changes of the particle sizes and the diameter was stabilized ca 120 nm after 1 week stirring. X-ray diffraction pattern of the TiO2 powder after the dryness without calcination indicates the dominant peak for anatase. Removal of the template was almost 36% after the alkaline rinsing by measuring its UV vis spectra of the washings. A buffered solution of Tris including viologen was irradiated through a xenon lamp under stirring in a quartz cuvett in Ar with or without the TiO2 with cut-off filter at room temperature. The formation of viologen monocation radical whose color is blue was easily recognized only in the reaction with TiO2. The formation of viologen monocation radicals from three types of (methyl, hexyl, and pentacarboxyl) viologens with time in the presence of the imprinted TiO2 and blank one was monitored spectrophotometrically. Blank means that it was fabricated similar way to the imprinted one without the template. Among these results, aliphatic C6 side chains of bipyridinium and terminal carboxyl groups were not effective to enhance. On the other hand, the less bulkiness methyl viologen resulted the highest yield. The most important result is that higher conversion was observed in every case of imprinted TiO2 compared with blank one. Therefore, the key point for recognition is not peripheral part, but bipyridinium part of the viologen.

Indium sulphide (In2S3) is a very promising semiconductor material for window layers in solar cell devices. It is currently being investigated for high efficiency solar cell based on Cu(In,Ga)Se2-In2S3 heterostructures. The chemical bath deposition (CBD) technique is one of the most convenient methods to obtain In2S3 films because of its simplicity, low cost and some other advantages. Amorphous and polycrystalline In2S3 films on glass substrates have been obtained by the CBD technique. Like in many others CBD processes, the deposition mechanism and kinetic growth of In2S3 films on glass substrates is not very well understood [1-6]. In this work we have chemically deposited In2S3 films for different times from 6 up to 39 hours, in order to study by atomic force microscopy (AFM) the formation of the films on glass substrates. The AFM measurements were performed in a liquid medium in which the cantilever tip and the sample are completely immersed in the liquid. A specially designed AFM cell is composed of a tip attached to a circular transparent window, the liquid level is between the upper and lower surface of the window, and a circular meniscus is established around the window, preventing the tip could be affected or destroyed by the surface tension of the liquid. By using this liquid AFM technique, we can at real-time observe the thin film forming process, and thereby clearly reveal the growing mechanism. It is an ideal and more practical tool for in situ investigation of samples which are normally found in liquid environments.

The paper deals with the study of PV module encapsulation using liquid methylmetacrylate composition hardened by UV radiation. The solar cells encapsulation method by methylmetacrylate composition in the glass-glass and glass PET-foil constructions of PV modules is investigated. The UV hardening modes of methylmetacrylate composition are investigated and developed. The studied method allows to eliminate heating during encapsulation and reduce the PV module production cost. The new method makes it possible to encapsulate solar cells on any substrates, including easily melted polymeric ones, and also in the glass-glass construction.

The structure and technological modes of liquid methylmetacrylate composition hardening during encapsulation have been investigated and selected. PV modules investigation for the resistance to external actions according to IEC61215 standard procedure provided positive results

Factors that determine the performance of dye-sensitized nanocrystalline solar cells are discussed

The stability of high performance thermoelectric Zn4Sb3 has been studied, by using synchrotron powder diffraction to establish differences in phase transition temperatures of two samples. High resolution multi temperature diffraction data has been collected, with a time interval of 13 months, and the phase transition temperature was determined based on the results of Rietveld refinements. The refinements show a difference in transition temperature from data collected the first time till data collected the second time. Furthermore the samples showed impurity peaks after being exposed to air for 13 months, indicating that the sample decomposes over time.

It has been empirically established that for quantum confined p-i-n solar cells a high electric field across the i-region is necessary for an optimal extraction of carriers from the well. This restriction imposes an upper limit for the total thickness of the i-region beyond which severe performance degradations are reported. For a given material system, the best efficiency trade-off is often achieved in the vicinity of this critical i-region thickness where the Voc degradation remains minimal and a higher photocurrent is afforded by the larger number of wells. But, even for devices that satisfy this condition, occasionally a severe Voc degradation occurs. Here, we show that this degradation is directly correlated to the carrier escape sequence from the wells and that a careful engineering of hole and electron confining potentials can be used to alleviate this shortcoming.

A non-contact metrology for electrical characterization of p-n junctions has been developed for use on photo-voltaic materials. By analysis of junction photo-voltage (JPV) measurements at multiple light beam modulation frequencies and multiple light penetration depths, a comprehensive electrical analysis of photo-voltaic materials is provided for junction sheet resistance, leakage current, capacitance and bulk carrier diffusion length. The JPV analysis can be made with screen and native oxides on the surface, so no pre-measurement chemical etching is required. Since the probe does not contact the p-n junction surface, measurements can be made in a continuous fashion with the junction moving under the probe, providing a method for efficient high-resolution mapping of local electrical properties. The non-contact probing also allows for non-damaging measurements in both “hard” (Si) and “soft” (organic) photo-voltaic materials. Examples of p-n junction properties in polished, crystalline-Si and cast poly-Si will be discussed.

Power conversion in thermophotovoltaic (TPV) or any other photovoltaic device can be increased by implementing monolithically series connected multi-bandgap structure in the device. The main concern for multi-bandgap material is the availability of different band gaps for the optimal operation of the device. Based on the recent work, GaAsN/InAsN superlattice lattice matched to InP has shown the potential of achieving band gaps in the range of 0.65-0.35eV at 300K, which is technologically important range for the TPV structure due to the availability of the photon energies in this range from the heat source. In this work, we will present the calculation details and results to find the maximum power generated by the multi-bandgap monolithically series connected devices. Optimized band gaps for p-i-n junction subcells were estimated by finding the optimal current to provide the maximum power through the series-connected double, triple and quadruple junction cells for 1350K blackbody radiation as an incident flux.