Hierarchically structured aggregates, consisting of TiO2 nanoparticles were produced via one-step solvothermal syntheses with a mixed solvent system containing both acetic acid and ethanol. Two of the resulting structures, one ~700 nm and the other ~300 nm in diameter, were found to be comprised of 8.5 nm and 10.5 nm anatase crystals, and possess specific surface areas of 138 and 106 m2 g−1 respectively. These particles were incorporated into Dye-sensitized Solar Cells (DSCs) as high surface area scattering layers, along with a layer of a transparent material. Solar-to-electric conversion efficiencies (PCE) of 9.1% and 8.2% were recorded using these aggregated particles as compared to those of commonly used large particles scattering layer 7.4%.
P25 is one of the most widely used forms of titanium(iv) oxide (TiO), routinely utilised in dye-sensitised solar cells (DSCs), where it is often employed as a control, in spite of its poorly defined nature and the typically low device efficiency (or possibly because of this). Work by Park in 2000 and later by Lin et al. suggests that the rutile component might not be to blame for this, as has often been claimed. Recently it has been observed that P25 has quite a sizable amorphous content. A method to selectively remove this non-crystalline material has been developed, allowing for scrutiny of the role this amorphous material plays. Here we compare hydrothermally treated P25 (H-P25) with the as-received material, realizing solar-to-electric conversion efficiencies of 5.3% and 3.2% respectively. More importantly, this reveals important information about the detrimental effect of amorphous TiO on DSC performance, with broader implications, as most researchers do not actively examine their synthesized materials for the presence of an amorphous component.
Dye-sensitised solar cells continue to be a promising photovoltaic technology for indoor and outdoor applications, with increased interest in power window applications integrated into buildings. This results from properties not seen in other, more established solar technologies, such as the range of available colours, partial transparency and good performance under low light intensities or in partial shade. In spite of the attractiveness of this application and the commercial availability of suitable non-scattering TiO2 materials, the vast majority of new TiO2 materials being developed and reported in the literature are dried prior to being made into a paste and subsequently into photoanode films. Here, we make a detailed side-by-side comparison of different paste-forming techniques, with one yielding scattering films, and the other yielding non-scattering films. Devices utilising the organic dye D149 showed comparable performance using both approaches (6.9% photovoltaic conversion efficiency (PCE) with drying versus 6.4% PCE without drying), while the difference was slightly more marked with the dye N719 (7.7% PCE versus 6.8% PCE), suggesting that the trade-off in light harvesting required for power windows may be acceptably small. We also discuss ways by which these differences may be further decreased.
In general, the transition elements, including Hafnium (Hf), have become the focus of researchers' attention, as when they combine with chalcogens and halides, they turn into semiconductors with distinct energy gaps. Moreover, chalcogens and halides are desirable in scientific research when forming layers or membranes. The Janus monolayer is unique two-faced material composed of two different chemical species on opposite sides of a single layer. Herein, we use first-principles simulations to thoroughly investigate the electrical and optical properties of this material. Our calculations reveal that the Bromochlorohafnium (HfClBr) Janus monolayer is an indirect semiconductor at equilibrium, with an energy gap of 0.928 eV and changing from 0.532 eV to 1.233 eV after applying the biaxial strain, as determined by the Perdew-Burke-Ernzerhof (PBE) method. The results indicate that the Janus HfClBr monolayer has a competitive advantage over other materials for use in solar cells and energy storage devices due to its unique optical and electrical characteristics. Furthermore, our analysis showed that the optical and electrical characteristics of the Janus HfClBr monolayer are significantly impacted by biaxial strain, with the ability to absorb light in both the visible and ultraviolet spectral regions. Additionally, the first optical gap of the Janus HfClBr monolayer is found to be shiftable under the biaxial strain, suggesting potential applications in nano-electronics, particularly in the field of solar cells.
Bismuth oxyhalide compounds have similar electronic configurations and crystal structures. Due to high electronegativity, they can be used for synthesizing solid solutions that have a number of advantages, which are enhanced charge separation, efficient adsorption, and high photoreduction potential. Solid solutions of the general formula BiOI1‐xFx (X=0 to 0.5) were prepared using the soft chemical method. The investigation of the optical properties of the considered solid solutions revealed a blue shift in wavelength. The solid solution BiOI0.7F0.3 exhibited an excellent adsorption coefficient and optimum photodegradation performance with RhB dye. Compared to pure BiOI, it showed higher adsorption and caused twice more efficient photodegradation. The different density functional theory (DFT) methods calculations revealed that the shift in band gap in the considered solid solutions mainly took the form of up‐shifting in the conduction band; thus, it was predicted that the reduction potential would increase with the increase in fluorine content. The results thus suggest that BiOI1‐xFx solid solutions are a viable alternative for the use in photocatalytic removal of toxic Pb2 ions from aqueous solutions.
We have considered the production of bromine isotopes by studying the cross-sections of nuclear reactions in the selenium enriched target. This is of importance due to the applications in nuclear medicine and radiation therapy. Eight channels are observed in the production of bromine isotopes: 7634Se(p, 2n) 7535Br, 7734Se(p, 3n) 7535Br, 7634Se(p, n) 7635Br, 7734Se(p, 2n) 7635Br, 7734Se(p, n) 7735Br, 7834Se(p, 2n) 7735Br, 8034Se(p, 4n) 7735Br, and 8034Se(p, n) 8035mBr. The energy of the interacting protons ranging from the threshold is 2.20–84.20 MeV and is calculated by using an activation technique. For the proton-induced production of bromine isotopes from selenium target atoms, the stopping power and the yield have been calculated. The Zeigler formula was applied to investigate the cross-sections and to determine the yield for each reaction over the stopping power range. The total energy of each reaction and the corresponding crosssections are statistically analyzed. These energies are reproduced by the incident proton energy with acceptable errors at 0.01 MeV intervals. One of the most significant results of the current calculations is the stopping power of targets evaluated within the Ziegler and SRIM approaches.
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