Studies On The Electrochemical Deposition In Organic System Of Mn-doped NiO Electrochromic Thin Films And Their Properties

As a kind of anodic electrochromic （EC） material, NiO performs well with highcolored efficiency, short response time, long service life and low cost. NiOelectrochromic film has broad application in many fields such as information,electronics, construction and national defense, which is considered to be one of the mostpromising anodic electrochromic materials. Electrochromism is a phenomenon thatmaterial can reversibly change their optical properties （transmission, reflection andabsorption） under an applied electric field. The development process, prepared methods,testing instrument and application of electrochromic materials were summarizedsystematically in this paper.NiO electrochromic film is still far from largr-scale practice application which candevelop into great functional materials under continious exploration and studies bymany researchers. Optimizing technological parameter and doping with other elementsare often used in improving electrochromic property at present. There are manymethods used for the preparation of NiO films, among them, electrochemicaldeposition （ECD） is the most optimal preparation process for its merits of uniformedfilm formation, simple equipments and large-scale formation of films. However, theECD in water system is difficult to dope the NiO film or to achive the codeposition ofmultiple metals. Hence, in this paper, Mn-doped NiO films were fabricated in organicsystem by electrochemical deposition with NiCl₂as main sault, MnCl₂as dapant,LiClO₄as supporting electrolyte, N, N-dimehtyl formamide （DMF） as organic solvent,and FTO conductive glasses as substrates. In order to change the structure of NiO filmand improve its EC properties, manganese（Mn）atoms were doped into NiO film.Mn-doped NiO films were prepaered under different conditions sunch as the molarratio of Mn and Ni in the organic solution, deposition voltage and deposition time. The optimized technological parameters were obtained by the comparation of the structuresand properties of the films prepared under diffenrnt conditions.Results showed that when the molar ratio of Mn and Ni in organic solution was1:10, deposition voltage was3.5V and the deposition time was15min, the Mn-dopedNiO film had excellent electrochromic properties with△T=88.5%and△OD=1.000,t_b/t_s=1.96/1.72s, R=1.08and EC=44.55mC·cm^-2. XRD analysis revealed that nickeloxide particles presented amorphous or polycrystalline state and UV-vis absorptionspectra showed that Mn doping improved the crystallinity of NiO film and decreasedthe energy gap along with enhancing the absorption property in near ultraviolet band,respectively. The Mn-doped NiO film exhibited excellent color memory and storageability in air. Unfortunatly, the film nearly lost electrochromic probility after5000thcycling in0.5M KOH solution, which needs to be further studied.