Zinc telluride is a gray or brownish-red powder that is a compound of zinc and telluride, with the chemical formula ZnTe. Ruby cubic crystals can be obtained by sublimation. Stable in dry air, it breaks down when exposed to water, releasing foul-smelling and toxic hydrogen telluride gas. Zinc telluride is mainly used in semiconductors and infrared materials, can be used as fluorescence materials and phosphorescent materials, but also can make light emitting diodes, infrared detection, radiation detection materials. Zinc telluride is transmittable to light with wavelength of 0.65μm and has a refractive index of 2.7 for light with wavelength of 1-8 μm.
The preparation of [2]
In the prior art, there are two methods for preparing zinc telluride, including dry and wet methods. The dry process is the synthesis of zinc telluride by heating tellurium and zinc to 1000 ~ 1200℃ in a closed atmosphere. In the wet process, sodium telluride reacts with zinc acetate in aqueous solution to produce yellowish-brown zinc telluride hydrate precipitation. However, the dry process takes a long time to consume, and the product quality of the wet process is difficult to guarantee. Moreover, in the process of preparing zinc telluride, if dilute acid is encountered, highly toxic hydrogen telluride (H2Te) will be released, which shows that the preparation of zinc telluride has a very high requirement.
CN201410198138.7 provides a preparation method of zinc telluride, the whole preparation process using high pressure synthesis method, short time, less equipment required, low excess coefficient, to a certain extent, reduce the production cost, improve production efficiency. In order to solve the above problems, CN201410198138.7 provides a preparation method of zinc telluride, including:
A, put tellurium and zinc mixed material into the graphite crucible, then pass through the inert gas to drain the oxygen, closed crucible;
B, put the crucible in a closed heat-resistant container, in addition to the oxygen in the heat-resistant container after the inert gas;
C. Adjust the pressure in the heat-resistant container to 0.6 ~ 3.0mpa, and the temperature rises to 1000 ~ 1500℃, and then hold it for 1 ~ 4h before cooling;
D. After cooling to less than 60℃, exhaust the air and relieve the pressure, and take out the mixed material to obtain zinc telluride.
Application of [3]
Zinc telluride can be used to fabricate a solar cell based on an array of oxygen-doped zinc telluride nanowires.
A oxygen doped zinc telluride nanowires array enhanced absorption in the middle of the solar cell structure, in the middle with solar battery technology, on the basis of nanowires for further enhance absorption layer with the light of the solar cell conversion efficiency, for the preparation of the high efficiency solar cells laid a solid foundation, is expected to achieve the next generation of solar cells to develop in the direction of high efficiency and low cost. The solar cells based on oxygen-doped zinc telluride nanowire arrays are in the following order from top to bottom: N-type AZO transparent conductive film coated with zno/O doped zinc telluride/zinc telluride three-layer coaxially coated nanowire array, (vertical) zno/O doped zinc telluride/zinc telluride three-layer coaxially coated nanowire array, PMDS support layer coated with the bottom of the nanowire and P-type doped high-conductivity monocrystalline silicon layer substrate. A vertical nanowire array with three concentrically coated layers of zinc oxide/oxygen doped zinc telluride/zinc telluride with intermediate band characteristics is used as the photoelectric absorption layer.
Electrodes are drawn from AZO transparent conductive thin film and P-type doped high-conductivity monocrystalline silicon layer, respectively. The height of oxygen-doped ZnTE nanowire array is 5-10 μm, the diameter is 100-300nm, the oxygen diffusion doping concentration in oxygen-doped ZnTE is 1-5%, and the diffusion layer thickness is 20-100nm. The thickness of zinc telluride is 10-50nm. Zinc oxide, oxygen-doped zinc telluride and zinc telluride form a coaxial coating structure, with zinc oxide in the outermost layer. The number of O 2 -doped Zn telluride nanowires per square micron of substrate surface should be more than 2 under high-resolution field emission scanning electron microscopes.
Preparation method: The physical vapor deposition of zno/O doped zno/Zn telluride/Zn telluride three-layer coaxially coated nanowire array was completed in a multitemperature tube furnace. The zinc telluride source is a powdered zinc telluride crystal located upstream of the air stream and in the center of the heating section of a temperature zone of the tubular furnace; The substrate for depositing ZnTE nanowires is located downstream of the ZnTE source and in the middle of a heating section in a temperature zone or between two heating sections; During the deposition process, multiple heating sections were heated up at the same time to ensure uniform and constant temperature distribution in the tube furnace, and the evaporation source temperature was maintained at 780 ~ 900℃ and the substrate temperature was maintained at 380 ~ 450℃ for 30 ~ 90 minutes to prepare uniform and defection-free zinc telluride nanowires. Gold or bismuth catalysts used for Zn telluride deposition are plated on the substrate used for Zn telluride deposition by electron beam evaporation or magnetron sputtering process, and then anneal to form particles with diameters of 25 ~ 100nm; The transport gas of zinc telluride for gas phase transport uses high-purity nitrogen. The flow rate is accurately controlled by the gas flowmeter from 50 to 200sccm, and the flow is from the source of zinc telluride to the substrate.
The Angle between the substrate surface and the gas phase transport zinc telluride is 50° ~ 80°. After the deposition of zinc telluride nanowires, the atmosphere in the tube furnace was replaced with a mixture of oxygen and nitrogen, heated up and maintained at 200 ~ 300℃ for 2 ~ 20 hours. Zinc oxide layer is formed on the surface of zinc telluride nanowires, and oxygen diffuses into the zinc telluride lattice to form an oxygen-doped zinc telluride layer. Zno/O doped Zn telluride/Zn telluride coaxially coated nanowires were formed. Zinc oxide/oxygen doped zinc telluride/zinc telluride coaxially coated nanowire arrays are fabricated by annealing zinc telluride nanowire arrays in a mixed atmosphere of oxygen and nitrogen.
The PDMS layer was prepared by injection molding process and wrapped on the bottom end of oxygen-doped zinc telluride nanowires. After injection molding, the top of the nanowires was exposed by oxygen ion etching. The thickness of the PDMS layer is based on the wrapped nanowire array. The thickness of the N-type AZO transparent layer deposited by pulsed laser is 2-10 μm. The AZO layer is wrapped on the top of the oxygen-doped zinc telluride nanowires. The light transmittance of the AZO layer is above 85%, and the resistivity of the AZO layer is on the order of 10-4 ω ·cm or lower. Oxygen-doped zinc telluride has an intermediate band energy level, which can not only absorb photons larger than the energy band gap, but also absorb photons with smaller energy through electron transitions of valence band-intermediate band and intermediate band-conduction band. At the same time, the nanowail structure greatly reduces the drift distance of photogenerated electron hole pairs under the action of internal electric field. It reduces the recombination probability of photogenerated electron holes and enhances the absorption and conversion efficiency of solar cells.
Beneficial effects: doped zinc telluride has intermediate band energy levels, which can absorb photons and generate electron hole pairs with high efficiency. At the same time, the nanowire structure reduces the drifting distance of photogenerated carriers and the recombination probability of photogenerated carriers, so the photoelectric conversion efficiency of this solar cell is much higher than that of traditional solar cells. The use of intermediate band nanowires in the invention can obtain higher photoelectric conversion efficiency compared with the commonly used thin film absorption layer. The experimental results show that the solar cell prepared by the above method has higher photoelectric conversion efficiency.
