Transition Metal Oxide Based Multifunctional Electrochromic Material

Electrochromic(EC)materials are intelligent materials that can selectively absorb or pass light under external electrical stimulation to achieve color change.Therefore,they are widely used in fields of energy saving construction and intelligent vehicles.Among them,inorganic EC materials attract researcher's attention due to its good cycle stability,large optical modulation window and good the memory effect.However,researchs of inorganic EC materials mainly focused on the modification of transition metal oxides,and rarely developed new materials or explored new functions over the past few decades.In order to break through this limitation,we systematically explored the EC phenomenon of chalcogenides quantum dots for the first time and successfully developed the application of inorganic EC materials from oxidation to sulfide.In addition,two kinds of multi-functional EC films based on transition metal compounds were synthesized in this work by being sensitized with chalcogenides or doped with rare earths.First,CdS quantum dots sensitized TiO2(TiO2/CdS)films not only show the performances of multi-color swithcing and infrared modulation for the first time,but also can be used to prepare quantum dots sensitized photoelectrochromic devices.Acting as an EC film,TiO2/CdS film exhibits a high optical modulation up to 79.2%and an ability of reversible switching among multicolors;Being used as photoanodes,TiO2/CdS films can work with WO3 EC electrode,Fe(CN)63-/4-redox couple to form a quantum dot sensitized photoelectrochromic device.By switching external circuit state,the device achieves reversible coloration and bleaching.In addition,the device also solves the problem of low transmittance and poor optical modulation of conventional photoelectrochromic device.Second,the rare earth element europium(Eu)doped WO3 film was successfully prepared by our group for the first time.As Eu3+ has a large amount of energy levels,the modified W03 film achieves significantly improved EC and tunable photoluminescent properties.Compared with pure WO3 films,Eu3+ doped WO3 film exhibits almost double enhanced optical modulation at 680 nm,and shortened coloration time by three times,and improved coloration efficiency by four times.In addition,Eu3+ ions doped WO3 film emits red fluorescence under the excitation of UV light.Especially,the fluorescence can be tuned by adjusting the coloration/bleaching state of WO3 film.The Eu3+ ions doped WO3 film exhibits a great potential in the preparation of illuminable "smart windows".In summary this work has not only broadened the research range of EC materials by synthesizing multifunctional inorganic EC materials based on transition metal oxides,but also crossed the research in many fields.This work provides a new way for developing electrochromism field.