In that report we observe the initial stages in the process of film growth at different irradiation doses. Investigations of influence of Mo deposition on glass substrates by means of self-ion-assisted deposition on its topography (atomic force microscopy) and wettability (sessile-drop method) were carried out. It was found out that with an increase of the irradiation dose, the average roughness and the contact angle increases rapidly at first and then decrease. 2.45-2.77 increase in the contact angle of water when Mo-based coating was deposited on the glass was observed.
Current-voltage (I-V) and capacitance-voltage (C-V) characteristics of photovoltaic, thinfilm p-ZnTe/n-CdTe heterojunctions have been studied in the temperature range of 280-400 K. The p-n junctions were grown by MBE on (100) semi-insulating GaAs substrates. From the analysis of I-V and C-V curves the potential barrier height of the junctions and its temperature dependence are determined. The relatively large value of the temperature coefficient of the potential barrier height (2.5-3.0 × 10^{-3} eV/K) indicates a high density of defects at the p-ZnTe/n-CdTe interface. The presence of interface defects limits the efficiency of the solar energy conversion of these devices.
We report on reduction of optical losses in n-CdTe/p-ZnTe thin-film solar cells grown by molecular beam epitaxy. The investigated thin-film devices were grown from elemental sources on monocrystalline, semi-insulating, (100)-oriented GaAs substrates. The optical losses have been reduced by a texturing of the device surface and by depositing of a ZnO antireflection coating. Current-voltage and spectral characteristics of the investigated p-ZnTe/n-CdTe solar cells depend significantly on the preparation of the surface of the ZnTe window. We describe a procedure of chemical etching of the ZnTe window leading to surface texturing. A ZnO layer of proper thickness deposited by low-temperature atomic layer deposition technique on the ZnTe surface forms an effective antireflection coating that leads to the reduction of optical losses. Due to reduction of the optical losses we observe increase of the short-circuit current, J_{SC}, by almost 60% and of the energy conversion efficiency by 44%.
The comprehensive analysis of transmission spectra for light propagated through ITO/ZnO/CdS multilayers to solar cell active layer of CdTe is performed. Optimal thickness of ZnO high resistive oxide supplying minimal optical losses in CdTe solar cell working range was determined. We get the maximal light transmission to active layer for ZnO film with thickness of 230 nm. The advantages of glass superstrate for multilayer structure with ZnO upper layer is discussed in comparison with the structure with ITO upper layer. Calculation of transmittance for textured surfaces of top face of solar element showed significant minimization of optical losses in the structure with ITO upper layer textured by inverted pyramids while for textured glass superstrate there is no ponderable profit as compared to multilayer structure with planar surface.
High-resolution X-ray diffractometer was used to study structural quality, lattice parameters and misfit strain in p-ZnTe/n-CdTe heterojunctions grown by the molecular-beam epitaxy technique on two different (001)-oriented substrates of GaAs and CdTe. The X-ray diffractometer results indicate that the CdTe layers, grown on lattice mismatched GaAs substrate, are partially relaxed, by the formation of misfit dislocations at the interface, and display residual vertical strain of the order of 10^{-4}. The presence of threading dislocations in the layers effectively limits the efficiency of solar energy conversion in the investigated heterojunctions. Homoepitaxially grown CdTe layers, of much better structural quality, display unexpected compressive strain in the layers and the relaxed lattice parameter larger than that of the substrate. Possible reasons for the formation of that unusual strain are discussed.
The main aims of this work were to produce and examine the characteristics of nanostructured ZnO in dye-sensitized solar cells. Parameters which are affected by the efficiency such as precursor materials, morphology were investigated. The Raman spectroscopy was used to investigate transformation from bulk material to solution. General morphologies and detailed structural characterizations were obtained using field emission scanning electron microscopy. X-ray diffractometer has been used to determine preferred crystal orientation and particle size of the ZnO nanostructures.
JavaScript is turned off in your web browser. Turn it on to take full advantage of this site, then refresh the page.