| In recent years,advances in technologies for flexible optoelectronic devices,including various displays,transistors and wearable devices,have laid more stringent requirement on highly transparent conductive materials.The most widely used transparent conductive film(TCF)in current industry is Sn:In2O3(ITO)thin films.However,indium is earth non-abundant and expensive.As an abundance and inexpensive alternative,Al:Zn O(AZO)continues to be a system of considerable interest,with sheet resistance and transparency values rivaling the most commonly used ITO.AZO also shows outstanding advantages such as non-toxic,easy preparation,and high stability etc.Furthermore,the insertion of metal(i.e.Ag)layers between transparent thin oxide films in an oxide-metal-oxide(OMO)sandwich configuration ensures superior opto-electrical properties with thinner conducting layers.Thin polymer materials,e.g.polyethylene terephthalate(PET)and polyethylene(PEN),are the leading candidates for flexible transparent substrates.However,there are some insurmountable limitations of the available polymer substrates,including low processing temperature,lack of dimensional stability during processing,and significant differences in the linear coefficient of thermal expansion(CTE)between the polymer substrate and the device films.Mica was used in this thesis as a new flexible transparent substrate.It seems that mica satisfies all of the requirements for such a substrate: low cost,optical transmittance of >90%in the visible,high temperature tolerance of up to 600 °C,a low CTE of ~1×10-6/°C(which matches those of silicon device materials),impermeability against oxygen and water,high dimensional stability,chemically inert surfaces parallel to the [001] planes and being flat at an atomic level,etc.Pulsed laser deposition(PLD)method was used to fabricate high performance ITO,AZO and AZO/Au/AZO transparent conductive films on Mica and PET.The film thickness,deposition temperature,oxygen partial pressure and annealing temperature were optimized based on the structure,surface morphology and the opto-electrical properties.The new TCFsystem was preliminary used as electrode for flexible transparent thin film heater and flexible perovskite solar cell applications.The main results could be summarized as below:(1)the microstructure and opto-electrical properties of ITO thin films were strongly dependent on the annealing temperature.The sheet resistance of 100 nm ITO thin film could reached 68 ? / ? when annealed at 300 ? C for 0.5 h,while the highest average transmittance reached a value of88.5% when annealed at 500 ?C.(2)The growth of AZO directly on muscovite mica via van der Waals epitaxy was established,as evidenced by XRD and RHEED patterns.Epitaxial AZO thin films(with a thickness of 100 nm)showed low sheet resistance of 21 ?/? and large average transmittance in the visible area(> 90%)with optimized process parameters.(3)The thickness of Au layer for AZO/Au/AZO photoelectric performance of multilayer film has a decisive influence,the best thickness is 12 nm.The top AZO film has an effect on surface roughness and the transmittance of the thin film;When the thickness is 50nm/12nm/50 nm respectively,the square resistance of samples can be as low as 1.4 ? / ?,average transmittance reached a value of 74.1%,quality factor is 3.565×10-2 ?-1.(4)The thin film heater of Mica transparent conductive material has some advantages,such as: the fast heating and cooling rate,the stability of the heating temperature,the cycle stability,and so on;it has a good application prospect on the the high temperature flexible transparent heaters.The efficiency of perovskite solar cell(ITO/Mica electrode)can reach 9.87%,it shows the potential applications. |
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