CN103303970B - Preparation method of band gaps adjustable magnesium-doped copper-zinc-tin-sulfur film - Google Patents

Abstract

The invention relates to a method for preparing a copper-zinc-tin-sulfur (Cu ₂ ZnSnS ₄ ) film whose bandgap is regulated by the concentration of magnesium impurities, which is characterized by using magnesium chloride, copper acetate, zinc acetate, stannous chloride, and thiourea as raw materials. Copper-zinc-tin-sulfur thin films with different magnesium contents were prepared by sol-gel technology. When the ratio of magnesium to zinc varies from 0 to 0.8, the corresponding band gap can vary from 1.54 to 1.22 eV. This method has a simple process , low cost, non-toxic and harmless doping elements, and can be used to prepare stacked solar cells with copper-zinc-tin-sulfur absorption layers with different band gaps.

Description

Preparation method of magnesium-doped copper-zinc-tin-sulfur film with adjustable band gap

technical field

The invention relates to a preparation method of a copper-zinc-tin-sulfur thin film whose band gap is regulated by a magnesium component. Magnesium chloride, copper acetate, zinc acetate, stannous chloride and thiourea are used as raw materials, and belongs to the field of thin film solar cell materials.

Background technique

Copper zinc tin sulfur is a direct bandgap compound semiconductor with an optical bandgap of 1.5 eV and an absorption coefficient of up to 10 ⁴ cm ^-1 on the high energy side of the absorption edge. It is used to prepare the absorber layer of thin film solar cells. Copper zinc tin sulfur is used as the absorbing layer, and its optical band gap is an important parameter to control the photoelectric conversion efficiency of thin film solar cells, especially tandem solar cells with different band gaps. At present, the method of adjusting the band gap of copper, zinc, tin and sulfur is to add selenium to copper, zinc _, tin and sulfur. and the human body are harmful. Therefore, it is of great significance to adopt a bandgap adjustment method that is non-toxic and harmless to the human body and has no pollution to the environment.

Contents of the invention

The purpose of the present invention is to overcome the environmental and health hazards caused by the current method of selenization to regulate the copper-zinc-tin-sulfur band gap. The invention adopts the selenium-free process to prepare the copper-zinc-tin-sulfur thin film with adjustable band gap.

The object of the present invention is implemented like this: copper acetate, zinc acetate, tin chloride, thiourea are dissolved in ethylene glycol methyl ether and ethanolamine according to stoichiometric ratio, keep under 45 ℃ of conditions, stir until completely dissolving, then Add thiourea and stir until completely dissolved to obtain a copper-zinc-tin-sulfur solution. Add magnesium chloride to the obtained copper-zinc-tin-sulfur solution according to the doping ratio, and stir until completely dissolved to obtain the copper-zinc-tin-sulfur solution with magnesium components. The prepared solution was dropped on the substrate placed on the spin coater, so that the solution spread evenly on the substrate. After spin-coating, dry at 300°C to evaporate the solvent, then repeat the process of spin-coating and drying several times to obtain a magnesium-doped copper-zinc-tin-sulfur film. Optical absorption spectroscopy tests show that the optical bandgap of Mg-doped CuZnSnS thin films is modulated by Mg doping concentration.

The advantages of the method for adjusting and controlling the copper-zinc-tin-sulfur optical band gap of the present invention are:

(1) The harm to the environment and human health caused by the selenization process is avoided.

(2) The optical bandgap decreases with the increase of Mg composition.

Description of drawings

Fig. 1 is a process flow diagram of the present invention.

Fig. 2 is an X-ray diffraction pattern of the magnesium-doped copper-zinc-tin-sulfur thin film prepared according to the present invention.

Fig. 3 is the optical absorption spectrum of the magnesium-doped copper-zinc-tin-sulfur thin film prepared according to the present invention.

Detailed ways

Example

Dissolve equal volumes of copper acetate, zinc acetate, stannous chloride, and thiourea at concentrations of 0.875 mol/L, 0.4375 mol/L, 0.4375 mol/L, and 1.75 mol/L in 30 ml of ethylene glycol methyl ether and 3 ml ethanolamine, at 45°C, stir until completely dissolved, then add thiourea and stir until completely dissolved. Measure 5 ml of this solution, add magnesium chloride with a ratio of 0, 0.1, 0.3, 0.5, 0.8 to zinc, stir until completely dissolved, and obtain a magnesium-doped copper-zinc-tin-sulfur solution. This solution was dropped on the substrate placed on the spin coater, spin-coated at a low speed of 800 rpm for 6 s, and then spin-coated at a high speed of 2500 rpm for 20 s. After the spin coating was completed, it was dried at 300 °C for 5 min, and then the process of spin coating and drying was repeated five times to obtain a Mg-doped copper-zinc-tin-sulfur thin film with a thickness of 2 μm. Figure 2 is the X-ray diffraction pattern of copper-zinc-tin-sulfur films with different magnesium components obtained after spin coating. The diffraction peaks are all copper-zinc-tin-sulfur phases, and no second phase related to impurities has been found, indicating that magnesium-doped The copper zinc tin sulfur is a single phase structure. Figure 3 shows the optical absorption spectra of copper-zinc-tin-sulfur thin films with different magnesium compositions. When the ratio of magnesium to zinc varies between 0 and 0.8, the optical band gap can be modulated between 1.54 eV and 1.22 eV.

Claims (3)

1. the preparation method of the magnesium copper doped zinc-tin-sulfur film that a band gap is adjustable, it is characterized in that with neutralized verdigris, zinc acetate, tin protochloride, thiocarbamide for raw material, be dissolved in ethylene glycol monomethyl ether and thanomin, obtain copper-zinc-tin-sulfur solution, magnesium chloride is added again in the copper-zinc-tin-sulfur solution obtained, finally the solution of acquisition is spun on substrate, after drying, obtains the copper-zinc-tin-sulfur film of magnesium doping.

2. according to the preparation method of the adjustable magnesium copper doped zinc-tin-sulfur film of a kind of band gap according to claim 1, when it is characterized in that the molar ratio of obtained the copper-zinc-tin-sulfur Chlorine in Solution magnesium and zinc acetate that contain magnesium is between 0 to 0.8, obtained copper-zinc-tin-sulfur film is custerite (Kesterite) structure.

3. according to the preparation method of the adjustable magnesium copper doped zinc-tin-sulfur film of a kind of band gap according to claim 1, when it is characterized in that the molar ratio of obtained the copper-zinc-tin-sulfur Chlorine in Solution magnesium and zinc acetate that contain magnesium is between 0 to 0.8, the optical band gap of the magnesium copper doped zinc-tin-sulfur film of acquisition can change between 1.54eV and 1.22eV.