INFLUENCE OF STRUCTURAL FEATURES OF ZNO FILMS ON OPTICAL AND PHOTOELECTRIC CHARACTERISTICS OF INVERTED POLYMER SOLAR ELEMENTS

In this work we investigated the effect of preliminary annealing of zinc acetate solution films on the morphology, structure, optical properties of the formed ZnO films and also on the photovoltaic properties of polymer solar cells based on the obtained ZnO films. It was found that the pre-annealing temperature significantly affects the morphology and structure of the obtained ZnO films. At pre-annealing temperatures below 200 oC the films have a strongly relief morphology (wrinkled morphology), while at pre-annealing temperatures above 200 oC the surface morphology of the films is smooth. The relief of ZnO films affects the photocurrent density of solar cells. Cells based on ZnO films with wrinkled morphology showed a higher photocurrent compared to smooth morphology, which is due to strong light scattering and, as a result, the optical path of light in the photoactive layer is increased due to multiple reflection of light in the wrinkled structure of ZnO. In addition, with increasing pre-annealing temperature, the photovoltage of solar cells and the rate of recombination of charge carriers increases, but the diffusion coefficient of charge carriers decreases, which indicates an increase in the density of defects in the crystal lattice of ZnO. Thus, it has been shown that smooth or highly relief thin ZnO films with controlled properties can be obtained from a zinc acetate solution.

Synthesis of ZnO material: A new approach by hydrothermal method

Zinc oxide (ZnO) material possesses various morphologies which have given ZnO many fascinating applications in practice. Thus, the controlled synthesis of morphology and size of ZnO microstructures has attracted great interest. Many synthetic methods exhibited their effectiveness in producing pure ZnO, and the hydrothermal synthesis expresses its own considerable advantages for controlling the morphology of ZnO with low particle-size distribution. Moreover, the hydrothermal synthesis can be performed under mild condition rather than the conventional harsh ceramic method. In this work, we performed hydrothermal synthesis by altering different initial seeds by pre-treating of Zinc acetate solution prior to hydrothermal action. Characterization methods such as X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman and Infrared (IR) spectroscopy were used to determine the morphology and surface functional groups of ZnO final products. Firstly, we processed the pretreatment of Zinc acetate solution by annealing it at 90 ◦C for 1h before putting the solution into autoclave together with NH3 solution for hydrothermal synthesis (this process is called as two-step hydrothermal synthesis). Secondly, the reaction temperatures (120 ◦C, 150 ◦C, 180 ◦C) were investigated to provide the role of temperature synthesis in controlling size and shape of ZnO, and at 150 ◦C, ZnO particles were formed with reasonable uniform morphology. Finally, we examined the effects of initial seeds by pre-treating Zinc acetate solution with H2O2, or, the initial seeds change from only Zn(OH)2 (without H2O2) to mutual existence of Zn(OH)2 and ZnO2 (with H2O2). In this case, ZnO Wurtzite phase was obtained with 100% purity at 180 ◦C, or at higher temperature than other samples whose ZnO Wurtzite phase was formed at only 150 ◦C. The results show that the nature of initial seeds greatly impact not only on the shape and size, but also on the surface functional groups of ZnO final product.

Flow Injection On-Line Distillation Method for Determination of Cyanide in Water

Purpose The flow injection distillation (zinc acetate solution) was changed to be 5% phosphoric acid in the method of determination of cyanide. Application Cyanide in groundwater was measured by FIA6000 + automatic flow injection analyzer directly. Results In the 2.0-100.0μg/L range, the linear correlation coefficient was greater than 0.9, the recovery was 86.1% -100.8%, relative standard deviation 1.3% -3.8%. Conclusion This method not only reduces the white crystals [Zn (OH)2] on the pump tube blockage, making the operation more simple and efficient, but also for the detection of a large number of groundwater samples.