The photoresponse behavior of one-dimensional ZnO nanowires (NWs) and nanotubes (NTs) grown on ITO-coated glass substrates via a wet-chemical route was investigated. The photoluminescence spectra exhibited a decrease in the deep-level intensity, indicating that the oxygen defects and impurities are occupied by the presence of N ions in the ZnO NT matrix after a nitrogen plasma treatment. I-V tests demonstrate an enhanced dark current (4.83 x 10(-7) A) after an extended plasma treatment of up to 900 s for ZnO NTs compared to that (0.571 x 10(-7) A) of NWs. Furthermore, the ZnO NTs show the highest reliable photoresponse, 20 times that of NWs under UV irradiation (325 nm) in air at room temperature. It is believed that nitrogen plasma ZnO nanotubes can potentially be useful in the designs of 1D ZnO-based solar cells and optoelectronic devices.
The CdS nanocrystals with different aspect ratios (ARs) can be synthesized directly in the presence of conjugated polymer poly(3-hexylthiophene-2,5-diyl) (P3HT). The UV-vis spectra of the composite films show a blue shift of the p-p * transition band with an increasing aspect ratio (AR) of the CdS nanocrystals, which was attributed to the destruction of the ordered structure of polymer chains as supported by PL measurements. Atomic force microscope measurements on P3HT/CdS film also demonstrate the aggre-gation of CdS nanocrystal in the P3HT matrix is more apparent for the CdS nanocrystals of AR 4 than that of AR 16, indicat-ing a stronger interaction between P3HT and CdS for a larger AR (16), which is favorable for the network structure and formation of percolation paths to increase the transport properties of the P3HT/CdS solar cells. Therefore, a higher power conversion effi-ciencies (PCE) up to 2.95 % can be obtained for the in-situ-grown P3HT/CdS with AR 16 upon annealing treatment at 160C for 60 min. VC 2011 The Electrochemical Society. [DOI: 10.1149/1.3585668] All rights reserved
We reported the fabrication of an FTO conducting thin film via a spray deposition method, which was used to investigate the effect of oxygen content in the carrier gas on deposited film morphology and properties. Using a carrier gas containing various O 2 /N 2 concentrations (0%, 20%, 50%, 80%, and 100%) led to significant changes in the thickness, size, and shape of grain growth. The deposited films with 0-50% oxygen content yielded a low resistivity of ∼10 −4 -cm and a transmittance in the range of 76-96% at 550 nm. Furthermore, by changing the carrier gas concentration, the FTO films displayed different charge transport, recombination, and collection properties due to the surface and interfacial effects. These films with modified properties can be applied to dye-sensitized solar cells (DSSCs). Overall, the conversion efficiency of a solar cell based on a 0% O 2 sample was increased by approximately 2% from that of a 100% O 2 sample. The higher efficiency is mainly the result of the lower O 2 content, which minimized the grain boundaries (spacing) and improved the electron transport on the FTO film surface.Transparent conductive oxides (TCOs) have many applications in modern electronics. Because of their high optical transparency and metal-like conductivity, they have been widely used for electrode applications in devices such as thin-film solar cells, 1 optoelectronic devices, 2 gas sensors, 3 frost-resistant surfaces, 4 e-windows, 5 etc. Up to now, most well-known TCO materials such as tin-doped indium oxide (ITO) exhibit n-type conductivity and oxygen deficiency due to oxygen vacancies and possible incorporated oxygen. However, ITO has two obvious disadvantages: (1) Providing a stable supply of ITO for the current expanding market is difficult because of the high price and scarcity of indium. (2) The electrical properties are significantly degraded after an essential annealing process in an oxidizing atmosphere with a temperature over 300 • C. Therefore, a substitution for ITO is needed. Fluorine-doped tin oxide (FTO) has been found to be one of most comparable materials to ITO. FTO has attracted much attention as a promising alternative because of its wide energy gap (E g = 3.67 eV), low cost of production, thermal stability, chemical inertness, and high transparency, although lower conductivities compared with the ∼10 −4 S/cm of ITO hinder its commercial applications. In addition, FTO thin films have been extensively prepared by various methods, such as chemical vapor deposition (CVD), metallorganic deposition, rf sputtering, sol-gel, and spray pyrolysis deposition (SPD). [6][7][8] Considerable effort has gone into investigating how to develop a textured surface on FTO conducting electrodes to improve the performance of solar cell devices by reducing light reflection or making light scattering more efficient. An anisotropic post-etching method using lithographic patterning and etching steps is typically used to achieve the desired morphology. 9,10 However, this might be deleterious to the film properties a...
In this study, tin oxide (SnO2) solution mixtures containing indium (In) of 0%, 3%, 7%, 15%, and 30% were used to fabricate In- and N-codoped SnO2 films on glass at 400 °C using an ultrasonic spray pyrolysis method combined with thermal annealing at 600 °C and post nitrogen plasma treatment. X-ray diffraction analysis demonstrated that the incorporation of elemental In in the SnO2 film primarily induces the evolution of crystalline phases from In-doped SnO2 to Sn-doped In2O3, depending on the doping concentration. Upon exposure to N plasma, the dark current dramatically increases in proportion to the treatment duration (5–40 min); the dark current can be enhanced for the 3% and 7%-doped samples by as much as 3 orders of magnitude compared to the untreated samples. Hall measurements confirmed that hole carriers could dominate the SnO2 host matrix to promote p-type properties at a low In content (3% and 7%) with an increase in resistance compared to undoped samples. However, samples with higher In content (15% and 30%) showed the opposite trend, due to the formation of a secondary phase of n-type In2O3. X-ray photoelectron spectroscopy was used to probe the incorporation and dissociation of chemical bonds between the doped In and N atoms in the SnO2. Moreover, depth profile measurements showed a correlation between the elemental compositions and elemental distributions of the codoped SnO2 film. Current–voltage (I–V) characterization revealed the improved behavior of heterojunction diodes consisting of a p-type (In, N)-doped SnO2 thin film deposited on n-type ZnO nanorod arrays.
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