Kegao Liu

The phases and morphology of CuInSe2 films prepared by different electrical deposition technologies

ABSTRACT CuInSe2 as one I-III-VI ternary compound with direct band gap, has become one of the most promising photovoltaic materials due to high optical absorption coefficient and conversion efficiency. CuInSe2 films were prepared by electrodeposition with CuCl2·2H2O, InCl3, SeO2 as raw materials. The phases of product films were analyzed by X-ray diffraction (XRD) and the morphology was characterized by scanning electron microscope (SEM). Experimental results show that dense and continuous CuInSe2 films can be obtained under conditions of deposition potential -0.5 V, pH 2.5 and raw materials ratio 6: 8: 12: 50, and the XRD diffraction peaks of CuInSe2 film are corresponding to (111), (220) and (311) crystal planes respectively, it consists of many rods with about 1 μm length; While the CuInSe2 film obtained under conditions of deposition potential -0.5 V, pH 2.0, and CuCl2·2H2O, InCl3, SeO2 and C6H5Na3O7·2H2O with concentrations of 6 mmol/L, 8 mmol/L, 6 mmol/L, 5 mmol/L respectively, shows different XRD diffraction peaks corresponding to (112), (220) and (312) crystal planes respectively, it consists of many non-uniform particles with diameters about 0.5-1.5 μm distribute on the film surface with dense, continuous and unsmooth morphology.

The Phases and Morphology of Bi2Te3 Films Prepared by Electrodeposition

Thermoelectric materials Bi2Te3 films were synthesized by electrodeposition using Bi2O3 and TeO2 as raw materials. The effects of electrodeposition technologies on formation of Bi2Te3 phase were investigated under different deposition conditions. The phases of obtained products were analyzed by X-ray diffraction (XRD) and the size and morphology were observed by scanning electron microscope (SEM). Experimental results show that, when the deposition potential increases from 0.7 V to 0.8 V, the Bi2Te3 phase can be gotten in the product film with good crystallinity while it increases up to −0.9 V particle shedding phenomenon occurred; The film deposited by Bi-Te ratio 1:5 has good crystallinity with the highest XRD intensity and sharp peaks by comparing different Bi-Te ion ratios. With the deposition time increasing, the XRD intensity becomes higher for Bi2Te3 phase in the product films obtained by depositing 4 min, 10 min to 15 min while lower for the SnO2 layer on the substrates. The product film obtained at 50°C has the highest crystallinity in the samples obtained at 30°C, 40°C and 50°C. Lactic acid was the best additive for improving the quality of product films. Uniform and dense Bi2Te3 film with good crystallinity and particles size of 200 ∼ 300 nm can be obtained under the deposition conditions of 50°C, −0.8 V, 15 min and Bi-Te iron ratio 1:5.

Characterization of the phases and morphology in synthesizing Cu2-xSe and CuSe films

ABSTRACT Copper Selenides are important semiconductor materials with excellent performance. Cu2-xSe and CuSe films were synthesized by spin-coating and chemical co-reduction method. The phases of product films were analyzed by X-ray diffraction (XRD) and the morphology was characterized by scanning electron microscopy (SEM), and the compositions of products were analyzed by energy dispersive spectroscopy (EDS). The surface resistance of the product film was measured using a four-probe resistance instrument. When Copper chloride was chosen as copper source, the products contain Cu2-xSe, CuSe and a small amount of NaCl. When the reacting temperature is below 180 °C, the XRD intensity of impurity phase NaCl is obviously increased, while it is easier to produce Cu2Se film at 200 or 220 °C. The sample obtained at 160 °C for 20 h consists of about 0.3 ∼ 0.5 µm particles, while the sample obtained at 220 °C shows about 2 ∼ 4 µm flake crystals; When the copper nitrate is used as a raw material, the XRD peaks of the product obtained at 200 °C for 20 h are much high and sharp, the phases obtained are mainly CuSe. The sample obtained at 200 °C consists of hexagonal flaky crystals with about 2 ∼ 3 µm diameters, while it consists of particles with about 0.3 ∼ 0.5 µm diameters for the sample obtained at 220 °C. In addition, the longer reaction time is conducive to the copper selenide formation, for example the single phase CuSe film can be obtained at 220 °C. The average resistivity of Cu-Se films synthesized at 200 °C for 20 h is 2.12E-3 Ω·cm.

Research progress in photolectric materials of CuFeS2

CuFeS2 as a photoelectric material, there are many advantages, such as high optical absorption coefficient, direct gap semiconductor, thermal stability, no photo-recession effect and so on. Because of its low price, abundant reserves and non-toxic, CuFeS2 has attracted extensive attention of scientists.Preparation method of thin film solar cells are included that Electrodeposition, sputtering, thermal evaporation, thermal spraying method, co-reduction method.In this paper, the development of CuFeS2 thin films prepared by co-reduction method and co-reduction method is introduced.In this paper, the structure and development of solar cells, advantages of CuFeS2 as solar cell material, the structure and photoelectric properties and magnetic properties of CuFeS2, preparation process analysis of CuFeS2 thin film, research and development of CuFeS2 in solar cells is included herein. Finally, the development trend of CuFeS2 optoelectronic materials is analyzed and further research directions are proposed.

Characterization of Bi2Se3 films prepared by electrodeposition and heat treatment

ABSTRACT Bi2Se3 as a semiconductor with narrow band gap about 0.24 eV has good thermoelectric properties. Bi2Se3 thermoelectric films were prepared by electrodeposition using Bi2O3 and SeO2 as raw materials, and the appropriate heat treatment process was adopted to improve the crystallinity of product films. The phases of product films were analyzed by X-ray diffraction (XRD) and the morphology was characterized by scanning electron microscopy (SEM), and the compositions of product films were analyzed by energy dispersive spectroscopy (EDS). The results show that the crystallinity of Bi2Se3 films can be improved significantly when heat treated at 350°C for 2 h or 400°C for 1 h. The XRD diffraction peaks are corresponding to (015), (1 0 10) and (110) crystal planes respectively. The surface of the product films shows particle aggregation, dendritic crystal and a few holes distributing irregularly.

The effects of different technologies on synthesis of CuInSe2 prepared by coreduction

Solution thermal method was used to synthesize CuInSe2 powders from metal chlorides and SeO2 at 160∼200°C. The phases of product samples were analyzed by x-ray diffraction (XRD), the size and morphology of the products were observed by JSM6380LA scanning electron microscope (SEM). The aim is to explore the best technology to obtain the pure CuInSe2 powders. Experimental results show that, CuInSe2 phase can be formed with metal chlorides by reacting for 20 h at 160°C, 180°C and 200°C and has XRD peaks corresponding to (112), (204) and (312) crystal planes, respectively. It consists of irregular spherical grains with about 0.2∼0.5 μm in diameter, which agglomerate larger particles with average particle size about 1∼3 μm. CuInSe2 phase was formed more easily at the temperature higher than 180°C and shows better crystallinity.