Preparation Of ATO Nanoparticle Dispersion And Application In Electrochromic Devices

In recent years,with the rapid development of thin-film solar cells,light-emitting diodes,flat-panel displays,touch screens,electrochromic and other optoelectronic devices,transparent conductive electrodes have been widely used as an important element.According to the characteristics of the film forming process,the preparation methods of transparent conductive electrodes are mainly divided into vapor deposition and chemical liquid deposition.Chemical liquid deposition is widely used in the preparation of various films due to its advantages such as simple equipment,easy operation,saving materials,being able to deposit on complex surfaces and patterning.Preparation of transparent conducting films by chemical solution deposition relies on transparent conducting oxide nanoparticle dispersions with small size,uniform particle size and high dispersion.The preparation of high-quality dispersions is mainly achieved by the steric hindrance effect of polymers or long-chain carbons organic molecular ligand.Long-chain molecules with higher boiling points are more difficult to remove in subsequent steps,which will damage the performance of the film.In this paper,it is proposed to disperse ATO nanoparticles using low-boiling small molecule amines as organic molecular ligands to obtain a uniform and transparent high-quality dispersion.The main research contents include the following aspects:1. Propylamine?PA?,ethylenediamine?EDA?,monoethanolamine?MEA?andtriethylamine?TEA?were used as ligand molecules to assist the dispersion of ATO nanoparticles in water.When no amine is added,the ATO nanoparticles quickly form precipitates and make the dispersion clear.The transparent and homogeneous ATO dispersions can be instantly obtained after the addition of amines.Taking MEA as an example,The ATO nanoparticles with Sb ratio ranging from 0%to 20%have good dispersion effect.The results show that the increase of Sb doping concentration is beneficial to the dispersion of ATO nanoparticles.For example,the size of Sn O₂secondary nanoparticles?Sb=0%?rangs from 12 nm to 84 nm with an average of about34 nm.When the doping ratio was 15%,the size distribution range is reduced to 9-55nm and the average particle size only 21 nm.2. The method of combining theoreticalcalculation and experimental characterization was used to study the interaction mechanism between small molecule amines and the surface of ATO nanoparticles.The adsorption of the selected amine molecules on ATO?110?surface was studied by the density functional theory calculation.The calculation results show that the nitrogen atom of PA,MEA and EDA forms a strong chemisorption with the Sb site on ATO surface.The bond lengths are around 2.23?.Since the TEA has a large steric hindrance,the N-Sb bond is elongated to 2.66?.The calculated adsorption energy data show that Sb doping is beneficial to increase the adsorption energy,which is consistent with the trend of the experimental results.In addition,XPS and NMR tests also confirmed the chemical adsorption of amines on the surface of ATO from the experimental point of view,that is amine molecules tend to form strong adsorption with Sb sites on the surface of ATO.The surface charge density of ATO nanoparticles increases after adsorbing amine,which causes strong repulsion between ATO nanoparticles,and finally achieves its rapid and effective dispersion effect.Taking MEA dispersed ATO nanoparticle suspension as an example,an ATO thin film was prepared by spin coating and used as a transparent electrode to prepare an electrochromic device.The prepared ATO transparent conductive film showed excellent performance.For example,at the standard wavelength of 550 nm,the transmittance of 10%Sb-doped ATO film reached 80.6%,and the film surface resistance was as low as 492?/sq.The prepared WO₃/ATO electrochromic device has a color difference of 50%during coloring and fading,and has good cycle performance.The research results show that this method has broad prospects in the preparation and application of ATO films.