| Electrochromic materials feature reversibly switching in optical properties by applying a low voltage.It can be colored or transparent in macro scale.They are mainly used in the fields of intelligent windows,automobile anti-glare rearview mirrors,displays,military camouflage,infrared camouflage and infrared thermal radiation control.In this thesis,a chemical bath deposition method is used to prepare NiO ultra-thin porous nanosheet structure film.The relationship between growth parameters and ion doping and the microstructure,surface chemical state and electrochromic properties of nanosheet films has been systematically investigated.The dynamic characteristics and discoloration mechanism of thin film electrochromism are comprehensively investigated.The main research results are as follows:(1)NiO porous nanosheet films are prepared on a fluorine-doped tin dioxide(FTO)conductive glass substrate by a facile room temperature chemical bath deposition method.The NiO film prepared under the optimized parameters has a unique porous structure,in which the optical modulation amplitude reaches 64%,the coloring time is 7.2s,the bleaching time is 1.3s,and the color change efficiency is30.6cm~2/C.Subsequently,the doping modification is carried out.In the optimized solution recipe,by adding different concentrations of ferrite under certain process conditions,the effect of iron doping on the microstructure and electrochromic properties of the NiO nanosheet films is determined.The results show that the pore size of the nanosheets increases with the increase of iron doping.Electrochemical tests in an alkaline environment show that the NiO nanosheet film with an iron doping content of 0.1%has the highest electrochromic performance among the doped samples,including high transmittance(98%)in the bleached state,high coloring efficiency(CE up to 49.8 cm~2/C),short response time(bleaching time is 1.2s,coloring time is 4.1s)and so on.According to the impedance test results,the doping of iron significantly reduces the impedance of the film which is an important cause for the improvement of the film performance.(2)The effect of titanium doping on the microstructure and electrochromic properties of NiO films is evaluated.The doped film still maintains the porous structure,and the doping of titanium can improve the crystallinity of the film.By adjusting the doping amount,it is found that the titanium doping amount is optimized as 0.2%.And an appropriate amount of titanium doping is beneficial to the improvement of the oxidability of Ni element,which is beneficial to the improvement of electrochromic performance.According to the spectral test,the optimal electrochromic characteristics can be obtained when the doping amount of titanium is set as 0.2%.The optical modulation range is up to 77%,the cycle stability is significantly improved(the contrast is still 61%after 500 cycles),the color efficiency is 42.6 cm~2/C,the coloring time is 9.8s,and the bleaching time is 2.3s.(3)The effect of co-doping of iron and titanium elements on the microstructure and electrochromic properties of the NiO nanosheet films are investigated.The nickel oxide film(NiO-Fe0.1Ti0.1)with 0.1%iron and 0.1%titanium co-doping demonstrates the highest optical modulation contrast.Composition analysis shows that iron is more easily doped into the NiO lattice than titanium.According to the results of the spectrum test,the contrast ratio of NiO-Fe0.1Ti0.1 is 63.94%,the coloring time is4s,the bleaching time is 1s,and the coloring efficiency is 48.85 cm~2/C.The cycle stability is better than NiO-Fe0.1 film but lower than NiO-Ti0.2 film,showing a complementary doping effect between the two elements. |
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