Classifications

• • G—PHYSICS
  • G02—OPTICS
  • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
  • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
  • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
  • G02F1/15—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on an electrochromic effect
  • G02F1/153—Constructional details
  • G02F1/155—Electrodes
• • G—PHYSICS
  • G02—OPTICS
  • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
  • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
  • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
  • G02F1/15—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on an electrochromic effect
  • G02F1/1514—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on an electrochromic effect characterised by the electrochromic material, e.g. by the electrodeposited material
  • G02F1/1523—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on an electrochromic effect characterised by the electrochromic material, e.g. by the electrodeposited material comprising inorganic material

Definitions

• the present invention is related to a new material of re ⁇ versible Lithium ion insertion electrode, trasparent and colorless in thin film, which remains colorless and trans ⁇ parent when Lithium is inserted.
• This material is particularly indicated as a transparent counterelectrode in electrochromic devices having variable transmission or reflection.
• An electrochromic device as per Figure 1 is composed by different layers in the followiny sequence: transparent support (1), colorless and transparent electronic conductor (2), electrochromic material (3), electrolyte (4), trans ⁇ parent and colorless counterelectrode (5) colorless and trans parent electronic conductor (6), transparent support (7).
• the transparent supports (1) and (7) can be made of glass or plastic material.
• the eletronic conductors (2) and (6) can be, for example, thin ln_0_ films tin-doped (ITO), Fluorine-doped SnO_ or ZnO .
• the electrochromic material (3) can be, for example, O,, Mo0 3 , Ti0 2 , necessarily0 5 , Prussian blue, polypyrol , polythiophene or any organic compound which can insert anions from the electro ⁇ lyte and operate wih Lithium salts in a thin film form.
• the electrolyte (4) can be liquid, for example, propylene carbonate in which a solid or liquid Lithium salt was dis- solved, preferably a polymer, for example, the polyethilene oxide complex, LiN (SOschreibCF_),.
• Lithium ion conductors are selected instead of protonic ones, because of the chemical neutrality of the former.
• the electrocoloration process corresponds to a reversible insertion reaction of Lithium ions in the electrochromic a- terial.
• a reversible electrochemical reaction is required in the counterelectrode, compatible with the electrolyte and the electrochromic material. This means that such a counter- electrode should be colorless, at least during the time the electrochromic material is in its colorless state.
• the ki ⁇ netics of this counterelectrode must be sufficiently fast in order that the response time, which corresponds to the necessary time period to obtain coloration or bleaching be of the order of the minute.
• the invention aims a counterelectrode material meeting the transparency properties, reversibility for insertion of Lithium ions and a sufficient kinetics to use it in an elec ⁇ trochromic device as described above.
• x is included between 0.2 and 0.8, and z is lower than 0.2.
• the reversible electrochemical reaction in this counter ⁇ electrode is the following: A ⁇ B C z 0 2 + ne " + nLi + ⁇ Z Z ZZ ⁇ Z ⁇ Z " ⁇ Li n A ⁇ B y C z°2
• Lithium ion radius which is 0.6A.
• the replacement of Cerium atoms with atoms of smaller ionic radius (Sn, Ti, Ge), which reduce the dimension of the insertion sites have the effect of increasing the difusion rate of Lithium in the material.
• elec trons hopping can occur over elements A, which have two stable valences.
• the incorporation of element C has the effect of increasing more and more the eletronic conduction by means of induction of valency. This conduction is favorable to a insertion reaction.
• This material can be deposited in a thin film form through different methods: sputtering or vacuum evaporation from the oxide AxByC z o £t itself, through the sol- gel process ou any other.technique of deposition of thin layer of mettalic oxide.
• the cyclic voltametry of Figure 2 has been achieved with the compound Ce 0 c ⁇ i n n ° deposited by the dip-coating method over a glass plate covered by a ITO film.
• the layer was prepared from a 0.25M Ti (0CH(Cl 2 ) d solution and 0.25M ( H) 4 ) 2 Ce (N0 3 ) 5 solution in ethanol. Velocity of withdrawal was lOcm/min. A thermal treatment of 15 minutes at 70°C, and 15 minutes at 450°C was then performed. The electrochemical characterization was performed in a 0.1M so ⁇ lution of Lithium propyleneperchlorate carbonate, in absence of humidity.
• the auxiliary eletrode was a platinum wire and the reference eletrode was constituded of a silver wire dipped in a 0.01M solution of propylene carbonate and silver perchlorate.
• the reference was separated from the main compartment by o porous plate.
• the obtained cathodic and anodic peaks are characteristic of a reversible insertion process.
• Figure 3 represents the fifth and fiftieth cycles of a potentiostactic cycling of the eletrode between-1.8V/Ag and 0.5V/Ag. This shows the insertion reversibility, since the inserted load is extracted from the material and has a very small variation between the fifth and the fiftieth cycles.
• Figure 4 represents the cyclic voltametry, performed at ambient temperature of an entire device: glass/ITO/Li n WO 3 /POE-TFSI/Ce 0 5 Ti 0 5 /lTO/glass
• This counterelectrode in comparison to the other ones above mentioned, has the advantage of showing a good transparency, a satisfactory reversibility as well as a fast insertion ki ⁇ netics. It can be used in a electrochromic device with vari ⁇ able transmission, but can also be used in a system with variable reflection, e.g. a rear-view mirror for automobiles In this case, it is enough to have a reflecting metallic layer behind the system.

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Cited By (5)

Citations (2)

• 1989
  • 1989-08-07 BR BR898904048A patent/BR8904048A/pt not_active IP Right Cessation
• 1990
  • 1990-08-06 WO PCT/BR1990/000006 patent/WO1991002282A1/en unknown

Patent Citations (2)

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