Doped Titanium Dioxide Films Prepared by Pulsed Laser Deposition Method

TiO2 was intensively researched especially for photocatalystic applications. The nitrogen-doped TiO2 films prepared by pulsed laser deposition (PLD) method were reviewed, and some recent new experimental results were also presented in this paper. A new optical transmission method for evaluating the photocatalystic activity was presented. The main results are (1) PLD method is versatile for preparing oxide material or complex component films with excellent controllability and high reproducibility. (2) Anatase nitrogen-doped TiO2 films were prepared at room temperature, 200°C, and 400°C by PLD method using novel ceramic target of mixture of TiN and TiO2. UV/Vis spectra, AFM, Raman spectra, and photocatalystic activity for decomposition of methyl orange (MO) tests showed that visible light response was improved at higher temperature. (3) The automatic, continuous optical transmission autorecorder method is suitable for detecting the photodecomposition dynamic process of organic compound

Research on anti-seepage grouting in completely weathered granite based on superfine materials

Objective To solve the problems of "draught without slurry", poor groutability and slurry stability in the grouting process of completely weathered granite, a new composite grouting material is proposed in this paper to improve the anti-seepage and mechanical properties of completely weathered granite. Methods Through a series of laboratory experiments, it investigates the effects of different water-solid ratios, superfine bentonite, and superfine Portland cement content on the engineering properties of grouting materials. The formation mechanism of the slurry were studied, and the optimal formula of the cement slurry was determined. The experiment revealed the action mechanism of the two superfine materials on the fluidity, stability, and stone body strength of the grout. Finally, the castability and effectiveness of the grouting material were verified by a field test. Results The results show that the composite slurry with a water-solid ratio of 1.2, a content of superfine bentonite and superfine Portland cement of 10%, and a content of ordinary Portland cement of 80% has good fluidity, stability, and resistance. The funnel viscosity was 35.5 s, the water separation rate was 2.4%, and the compressive strengths at 7 d and 28 d were both greater than 5 MPa. The compressive strength and the content of superfine bentonite in the composite material play a leading role in the properties of the slurry. The content of superfine bentonite and the morphology and distribution of its hydrated colloids determine the stability of the slurry, while an appropriate amount of superfine Portland cement increases the content of fine particles, making it easier for the cement to fill the gaps between the particles and improving the injectability of the slurry and the strength of the stone body. Conclusion The composite grouting material has excellent performance in the field test and good grouting performance. The wall formed after grouting meets the design requirements in terms of the anti-seepage effect and reinforcement performance

Optical Properties of Two-Dimensional/Three-Dimensional Composite Perovskite Films

Two-dimensional/three-dimensional (2D/3D) composite perovskites (CPs) are extremely promising for their application in optoelectronics. Although understanding the fundamental optical properties of 2D/3D CPs is of great importance for optimizing the performance of optoelectronic devices, relevant studies still remain far from being sufficient. In this work, by using R-methylbenzylammonium (R-MBA) and R-1-(1-naphthyl)ethylammonium (R-NEA) as the A-site cations, we have synthesized two kinds of 2D/3D CP films, abbreviated as R-MBA- and R-NEA-films, respectively. Impressively, with an increasing temperature from 80 to 300 K, no phase transition or obvious emission shift is observed in both R-MBA- and R-NEA-films, and the latter has stronger electron–phonon coupling strength. Femtosecond transient absorption spectroscopy reveals that the R-NEA-film exhibits faster hot carrier cooling time and shorter biexciton lifetime. This work not only confirms the possibility of regulating the optical properties of 2D/3D CPs by the use of different organic A-site cations but also provides important information for the development of related optoelectronic devices

Energy Band Alignment by Solution-Processed Aluminum Doping Strategy toward Record Efficiency in Pulsed Laser-Deposited Kesterite Thin-Film Solar Cell

International audienceKesterite-based Cu(2)ZnSnS(4) (CZTS) thin-film photovoltaics involve a serious interfacial dilemma, leading to severe recombination of carriers and insufficient band alignment at the CZTS/CdS heterojunction. Herein, an interface modification scheme by aluminum doping is introduced for CZTS/CdS via a spin coating method combined with heat treatment. The thermal annealing of the kesterite/CdS junction drives the migration of doped Al from CdS to the absorber, achieving an effective ion substitution and interface passivation. This condition greatly reduces interface recombination and improves device fill factor and current density. The J(SC) and FF of the champion device increased from 18.01 to 22.33 mA cm(-2) and 60.24 to 64.06%, respectively, owing to the optimized band alignment and remarkably enhanced charge carrier generation, separation, and transport. Consequently, a photoelectric conversion efficiency (PCE) of 8.65% was achieved, representing the highest efficiency in CZTS thin-film solar cells fabricated by pulsed laser deposition (PLD) to date. This work proposed a facile strategy for interfacial engineering treatment, opening a valuable avenue to overcome the efficiency bottleneck of CZTS thin-film solar cells

The structural, optical and thermoelectric properties of single target sputtered Cu2ZnSn(S,Se)(4) thin film

International audienceCu2ZnSn(S,Se)(4) (CZTSSe) thin film was fabricated by radio frequency magnetron sputtering single CZTSSe target without post-selenization or sulfuration. The formation of kesterite-type CZTSSe films with a nearly stoichiometric composition after in-situ annealing at 673 K can be achieved. The valence of the elements in CZTSSe films are Cu(I), Zn(II), Sn(IV), S(-II) and Se(-II). Optical transmission and absorption spectroscopy measurement reveal high absorption and the energy band gap is about 1.44 eV. The CZTSSe thin film is of p-type conductivity and high Seebeck coefficient value is of 450 mu V/K