Preparation Of SnO₂-based Bilayer Films By Ultrasonic Spray Pyrolysis And Study On Photoelectric Properties

Transparent Conducting Oxides(TCO)films are widely used in the fields of low-emissivity glass,photovoltaic solar cell modules,thin-film resistors,transparent thermal conversion films and flat panel displays because of their transparency and conductivity in the visible wavelength band at the same time.Among TCO films,fluorine doped tin dioxide(Sn O₂:F(FTO))films have been widely studied and applied because of their chemical stability,high hardness,good electrical conductivity,and low cost.It should be noted that the conductivity and visible light transmission of FTO films are mutually suppressed,and good optoelectronic properties are urgently needed when applied to many optoelectronic devices.How to obtain the optimization of the comprehensive optoelectronic properties of FTO films and to ensure the high visible light transmission of FTO films while reducing their square resistance as much as possible is an important topic.Common methods for the preparation of FTO films include vacuum vapor deposition,magnetron sputtering,pulsed laser deposition,sol-gel method,atomic layer epitaxy,ultrasonic spray pyrolysis(USP)method,and so on.Compared with other methods,the USP method has attracted a lot of attention because of its unique advantages such as simple device,no vacuum environment,good controllability of process parameters,large-area deposition,and low cost.How to take advantage of the ultrasonic spray pyrolysis method to prepare high-quality films at lower cost is anotherIn this thesis,we adopt the homemade ultrasonic spray pyrolytic spraying film preparation system to carry out the exploration of FTO film growth parameters,the exploration of the composite mechanism of FTO-based bilayer composite films and the optimization of their preparation,and apply them to the field of electrothermal conversion films.The details are as follows.(1)Based on the principle of ultrasonic atomization pyrolytic spraying preparation for thin film deposition,an ultrasonic atomization pyrolytic spraying thin film preparation system suitable for Sn O₂-based thin film growth was designed,assembled and commissioned.The problems of atomized sheet contamination by precursor solution,unstable atomization output,inaccurate temperature control and poor film uniformity were mainly solved.The Sn O₂-based films prepared by this system have good crystallization properties and surface flatness,and are highly grown along the(200)crystallographic plane in a meritocratic orientation.(2)To explore the suitable process parameters for the growth of FTO films.The polycrystalline FTO films were successfully prepared in quartz glass using Sn Cl₄·5H₂O and NH₄F as mixed solutions as precursors,and the effects of F doping concentration,substrate temperature on the structure,morphology,and optoelectronic properties of the FTO films were investigated,and finally we found that when n(F):n(Sn)=20 at%and the substrate temperature of 425°C,the film has the optimal optoelectronic performance with a visible light transmission rate of 74.56%,a square resistance of 11.03?·?^-1,and a performance index of 4.84×10^-3?^-1.(3)The antimony-doped tin oxide(Sn O₂:Sb,referred to as ATO film)was prepared on the FTO film by ultrasonic atomization pyrolysis spraying method,and the ATO/FTO composite film was obtained.The effects of ATO film layer thickness on the structure,surface morphology and optoelectronic properties of ATO/FTO bilayer composite films were investigated to explore the composite film compounding mechanism.The results show that as the thickness of the top ATO layer increases,the crystallization performance of the film is enhanced,the grain size increases and the distribution becomes more uniform,the square resistance first decreases and then tends to level off,and the transmittance first increases and then decreases.In a comprehensive view,when the thickness of the top ATO layer is 860 nm,the composite film has the best photoelectric performance with a transmittance of 76.2%,a square resistance of 4.75?·?^-1,,and a performance index of8.56×10^-3?^-1.(4)To study the electrothermal performance of FTO and ATO/FTO composite films,the films were subjected to 0-20 V electrical heating experiments.The results showed that the average heating time of the FTO film was 108.50 s,the heating efficiency was3.66×10^-4 W/(?·mm²),and the maximum heating temperature reached at 20 V applied voltage was 265.7?.When the thickness of the ATO film layer was 860 nm,the heating time of the composite film was shortened to 74.32 s,the heat generation efficiency was improved to 3.04×10^-4 W/(?·mm²),and the maximum equilibrium temperature reached at20 V was 440°C.(5)In order to investigate the high temperature thermal stability of the films,15thermal cycles were conducted for the FTO and ATO/FTO composite films under 20 V applied voltage.The maximum equilibrium temperature reached was 265.7?and the minimum temperature was 239.0?,with a temperature variation of over 10.05%.For the composite film,the top layer of ATO film has good high temperature thermal stability,which can play a good role in protecting the composite film.The temperature variation is kept within 3.3%,which has better electro-thermal stability performance.