Electrochemical preparation method for ZnS nanocrystalline semiconductor precursor film or semiconductor film

Abstract

The invention relates to an electrochemical preparation method for a ZnS nanocrystalline semiconductor precursor film or a semiconductor film. Electrolyte contains Zn<2+>, S2O3<2->, surfactant and SO3<2-> at the molar ratio of (15-20):(15-25):(0.2-0.8):(0.3+ / -0.1) as well as lithium chloride; the pH value of the electrolyte is between 2.5 and 4.5; then, the eutectoid crystallization of two elements Zn and S is realized with a constant-current method or a constant-potential method to generate a pure ZnS precursor film with a hexagonal-phase or cubic-phase structure; the obtained precursor film is kept at the constant temperature of 250-500DEG C for a period of time under the inert atmosphere protection condition; and a pure cubic-phase ZnS nanocrystalline semiconductor film with the advantages of high orientation and better crystallinity can be obtained. The method provided by the invention has the advantages of strong controllability and good repeatability. The prepared ZnS nanocrystalline semiconductor film is free from impurities and is suitable for the window layer material of a film solar cell.

Description

technical field [0001] The invention belongs to the field of photoelectric materials, and in particular relates to an electrochemical preparation method of a highly oriented ZnS nanocrystalline semiconductor thin film that can be used as a solar battery window layer material. Background technique [0002] ZnS is a direct bandgap semiconductor material of II-VI compounds, non-toxic, chemically stable, and has two common crystal structures, namely the wurtzite structure of the hexagonal phase and the sphalerite structure of the cubic phase. At room temperature, the band gap of hexagonal ZnS is between 3.74 - 3.91 eV, and that of cubic ZnS is between 3.54 - 3.72 eV. Such a wide band gap makes ZnS of these two structures exhibit good absorption in the ultraviolet region and good transmission in the visible region (transmittance higher than 80%). In addition, ZnS has high reflectivity in the near and mid-infrared region, so it has good thermal stability. These physical properti...

AI Technical Summary

Problems solved by technology

Among them, the chemical bath method is the most commonly used method. This method has simple process, low cost and mild reaction conditions, but has the following disadvantages: i) low efficiency and time-consuming; ii) poor reproducibility, which may be due to the concentration of the solution and The temperature distribution is prone to inhomogeneity, there are complex interactions between ions and the intervention of homogeneous precipitation, etc.; iii) The prepared ZnS nanocrystalline film has poor uniformity, low transparency, poor adhesion on the substrate, and is easy to crack The reason is that in the process of preparing ZnS nanocrystalline film by chemical bath method, homogeneous precipitation reaction is easy to occur, so that dense and heavy amorphous precipitates or crystalline precipitates of large particles are slowly precipitated in the whole solution, and these precipitates are inevitable. into the ZnS film, affecting the quality of the film

However, the literature reports on the preparation of ZnS nanocrystalline thin films by electrochemical methods are still very limited, and the preparation process of thin films has the following problems:

[0005] i) It is difficult to prepare pure ZnS nanocrystalline films

Because the standard deposition potentials of Zn and S are quite different (-0.76 V and +0.5 V, respectively), it is not easy to co-deposit to form pure ZnS, and because the free energy of formation of hexagonal phase and cubic phase ZnS is very close, Therefore, it is easy to generate mixed-phase ZnS; ii) Most of the prepared ZnS nanocrystalline films do not have a high preferred orientation, and when assembled into solar cells, it is not conducive to the rapid transport of photogenerated carriers in it; iii) The electrolytic method for preparing ZnS Most of the liquid contains Zn 2+ and S 2 o 3 2- The acidic solution has poor stability, because S 2 o 3 2- S is prone to occur in an acidic environment without other additives 2 o 3 2- + 2H + → S + H 2 SO 3 reaction, white S colloidal particles are generated, which makes the solution turbid, affects the stability of the electrolyte system, and ultimately affects the controllable preparation of ZnS nanocrystalline thin films.

Images