Study On Electrochromic And Infrared Radiation Modulation Performance Of The Polyaniline Films And Devices

Electrochromic materials can reversibly change their optical properties under applied voltages,exhibiting broad applications in intelligent camouflage,smart windows,information displays,and energy storage.Polyaniline(PANI)as an electrochromic material has attracted widespread attention due to its advantages of wide-band tunability,high optical contrast,etc.For potential application of PANI-based materials in visible-infrared multi-band intelligent camouflage,and solving the problems of insufficient infrared modulation,slow response speed,and poor cycling stability of PANI,PANI composite materials were constructed using sulfuric acid(SA)as the basic acid dopant,and functional dopants with abundant active sites to enhance the electrochemical performance of PANI films.A reflective infrared electrochromic device was designed to improve infrared modulation performance,response time,and cycling stability.Firstly,copper(Cu)ions doped PANI was proposed to study the effects of different concentrations of doped Cu ion on the infrared electrochromic performance of PANI thin films.The Cu-doped porous PANI films were prepared by chronoamperometry polymerization on a gold/polyether sulfone(Au/PES)porous substrate.By optimizing the doping concentration of Cu ions,the Cu-doped PANI film with a suitable roughness surface and high porosity was obtained.It was found that Cu ions could form Cu-N coordination with imine nitrogen atoms on the PANI main chain,increasing the ratio of polarons and bipolarons on the PANI chains from 56%to 66%,improving the absorption of PANI films in the infrared band effectively,and enhancing infrared modulation capability.The Cu-doped PANI infrared electrochromic device was prepared by using the prepared film as a functional layer.Compared with the SA-doped PANI device,this device showed improved reflection modulation from 10%to32%in the wavelength ranges of 400-1000 nm,consistent with the yellow or green background.The emittance variation(Δε)of the device in 8–14μm increased from 0.24 to 0.32,implying the improved electrochromic and infrared modulation ability.To accelerate the switching of PANI films in different states,carbon dots(CDs)were introduced as dopants,and PANI/CDs composite films were prepared by chronoamperometry method to further enhance the infrared modulation ability and response speed of PANI materials.Results revealed that SA with tetrahedral structures and the oxygen functional groups on the surface of CDs could form hydrogen bonds andπ-πinteractions with the PANI chains,facilitating formation of the highly oriented lamellar PANI structures with short-range disorder in-plane.The contact area between the film and the electrolyte was enlarged,and rapid switching between different states of the films was achieved.By optimizing the polymerization charge of the composite films,PANI/CDs composite films with excellent electrochemical performance were prepared.The assembled infrared electrochromic device presentedΔεof0.39,0.41,and 0.37 in the wavelength ranges of 3–5μm,8–14μm,and2.5–25μm,respectively.The response speed increased by over 30%.Furthermore,PANI/GQDs composite films were synthesized using graphene quantum dots(GQDs)as dopants to improve cycling stability and energy storage performance of the corresponding device.It is found that the abundant oxygen-containing functional groups on the surface of GQDs can form hydrogen bonds andπ-πinteractions with the PANI chains,beneficial to the loose and porous film structures,and increasing the contact area between the film and the electrolyte.The formation of conjugatedπbonds between GQDs and PANI can enhance rigidity between PANI molecular chains,improving stability of the composite material.Density functional theory(DFT)calculations proved that the ion migration performance of composite material was improved,thereby enhancing the electrochemical performance of the composite film.Finally,based on the advantages of PANI/GQDs films in infrared electrochromic and energy storage performance,the infrared electrochromic-supercapacitors dual-functional device was proposed for the PANI/GQDs composite material.The device can achieve color change from yellow to green and deep black in the visible light band,indicating the stored energy intuitively.TheΔεvalues in the wavelength ranges of 3–5μm,8–14μm,and 2.5–25μm are 0.38,0.45,and 0.4,respectively.And the area capacitance is 522 m F/cm~2@1 m A/cm~2in the voltage window of-0.8 V to 0.8 V.Moreover,the response time for coloring and blanching of the device is 2.5 and 2.1 s,respectively.After 200 cycles,the retention rate of current density for the device can achieve 98%,implying the improved cycling stability of the device.