Solution-based Preparation And Electrochromic Properties Of Nickel Oxide Thin Films

Electrochromic(EC)means that the optical properties(transmittance,reflectance,etc.)of the materials reversibly changed due to the change of electric field,thereby causing the change in material color reversible.The electrochromic material on the substrate is as a single electrode,and the electrolyte between the two single electrodes can be formed into a complete electrochromic device(ECD).Currently,ordinary glass on the building has good optical transmissive performance,which also transmits energy while ensuring good lighting,but the transmission of rays and energy cannot be dynamically regulated.The smart window being attached to the electrochromic material is not only a common glass function,but also dynamically change the glass color in an active manner,which functions as a light and heat shielding insulation,thereby achieving photothermal adjustment,energy saving and environmental protection,intelligent control.At the same time,electrochromic is also applied to the vehicles,giving the window smart discoloration function,making people's travel more comfortable.In addition,the smartphone back cover can also achieve electrochromic function to meet people's aesthetic needs.At present,it is found that there are many materials with EC characteristics,such as the regular metal oxides,metal complexes,organic small molecules,and conjugated polymers and so on.Nickel oxide in the Group?and Tungsten oxide located in the?B group are the most typical inorganic EC material.The Ni O film is often composed of a complementary device with WO₃due to the smaller light modulation,synergistic to achieve color regulation.In order to improve the Ni O film's optical modulation,two commonly used and simple methods are used to prepare Ni O films,and their electrochromic properties are tested and characterized,and electrochromic properties are optimized by doping,microstructure adjustment.The 0.1Sn-Ni O,0.2Sn-Ni O,0.3Sn-Ni O film of n(Sn):n(Ni)is 1:10,2:10,3:10,respectively,were prepared by sol-gel method.By comparing the optical modulation and the switching time,we found that,within a certain range,the smaller the annealing temperature,the greater the film optical modulation.In addition,the larger the driving voltage,the optical modulation of the Ni O film increases,but on the other hand,the driving voltage should be as small as possible in consideration of energy saving and film's cycle life.After contrast,the0.1Sn-Ni O film's optical modulation was found to be 79.1%at-2.43V?2.0V voltage,the coloring time was 25s,and the bleaching time was 20s,and the cycle life can be stably 1000s.In optical modulation performance,tin-doped Ni O film(0.1Sn-Ni O)is significantly increased than no doped Ni O film.Further,since the surface of the Ni O film prepared by the sol-gel method is uniformly dense,it is not conducive to the embedding/extracting of ions such that the film's switching time is longer.In order to shorten the film's switching time,this thesis prepare Ni O film with sheet-mesh structure by chemical bath deposition.The switching time of the film is largely affected by the surface morphology of the film.Since the hole in the surface of the Ni O film is the aisle of ion-embedding/extracting from the electrolyte,it is a key to the oxidative reaction,so the switching time is largely affected by the surface morphology of the film.The sheet-mesh structure of the surface of Ni O film can be described in terms of the shape,size,number,and uniformity of the hole formed by the sheets.The more suitable of the holes,and the bigger number of the holes,the greater optical modulation of the Ni O film.The Ni O film reacted over 5 min has a large optical modulation,and change the annealing temperature of the film find that the Ni O film annealing at 300°C has better circulatory stability.However,its performance has not reached the optimal state,and it is still need to be improved in switching time and cycle life.It is expected to enhance the adhesion of the film on the substrate while providing an embedding/extracting passage by constructing a nano core-shell structure.