KR20110066382A - Solid state polymeric electrolytes containing hole transporting moieties for low-cost dye-sensitized solar cell applications - Google Patents

Abstract

PURPOSE: Solid electrolyte for a dye-sensitized solar cell is provided to ensure high ionic conductivity, thereby increasing open-circuit-voltage and short-circuit-current and improving optical conversion efficiency. CONSTITUTION: Solid electrolyte for a dye-sensitized solar cell includes a hole transport material(HTM) of the structure of chemical formula 1. In chemical formula 1, R1 is C2~C8 linear or branched alkyl group; R2 is C1~C8 linear or branched alkyl group; R3 is C1, C2 or C3~C6 linear or branched alkyl group; X is O and NH group; and a and b are a molar ratio and a+b=1.

Description

Fabrication of Polyethylene Oxide Solid Electrolytes Containing Hole Transporting Materials for Low-Cost Dye-Sensitized Solar Cells {Solid State Polymeric Electrolytes Containing Hole Transporting Moieties for Low-Cost Dye-Sensitized Solar Cell Applications}

The present invention relates to a polymer electrolyte including a hole transporting material (HTM), a new type of hole transport material used in solar cells.

     Due to environmental and energy issues such as fossil fuel depletion, environmental pollution, CO2 and SO2 generation, solar energy is in the spotlight as the next generation of environmentally friendly alternative energy as infinitely clean energy. Solar cells are devices that can directly convert sunlight into current (voltage), and research on low-cost organic solar cells other than p-n junction solar cells using p-n junctions of existing inorganic semiconductors is actively underway. The advantages of organic solar cells, besides being inexpensive and environmentally friendly, are transparent, thin and light properties that can realize in-door applications and power windows. Dye-sensitized solar cells (DSSCs) are used for dye-sensitization solar cells using dye-sensitization by adsorbing dyes absorbing visible light in a semiconductor having a wide bandgap. to be.

      DSSC was first developed in 1991 by the Gratzel Group, Switzerland, by adsorbing Ru (II) -based complexes on TiO2 metal oxides with optically transparent nanoparticle sizes (15-20 nm). It consists of a metal oxide, dye photosensitive agent, electrolyte, and an electrode.

     Specifically, transparent conducting oxide electrodes such as fluorinated tin oxide (FTO) and indium tin oxide (ITO), and nonoparticulated oxide semi-conductor layers such as TiO2 and ZnO, ruthenium and It consists of dye-sensitizers such as inorganic or organic dyes, electrolytes containing electrolytes and redox couples, and metallic catalysts such as platinum that acts as counter electrodes.

     The principle of operation of dye-sensitized nanoparticle oxide solar cells is that when the sunlight (visible light) is absorbed, dye molecules generate electron-hole pairs, and electrons are injected into the conduction band of the semiconductor oxide. Electrons injected into the semiconductor oxide electrode are transferred to the transparent conductive film through the interface between the nanoparticles to generate a current. The holes produced in the dye molecules receive electrons by the redox electrolyte and are reduced again to complete the solar cell by operating the dye-sensitized solar cell.

However, in the dye-sensitized solar cell, a kind of electrolyte mainly used includes a liquid electrolyte and an ionic liquid electrolyte. However, it exposes the following problems. That is, dyes adsorbed on the surface of TiO ₂ by ester bonds can be desorbed by nucleophilic substitution reaction with iodine ions at high temperature, and if the sealing is not good, electrolyte solution evaporates or water molecules or oxygen molecules in the air penetrate. This can reduce the efficiency by reacting with the electrolyte, causing problems in the stability of the device, or can not be electrically connected while chemically separating a plurality of cells on a single substrate (substrate), the size of the strong corrosive iodine At about 0.2 nm, not only the porous TiO ₂ but also the surface of the electrode can be reached, which is a problem in the stability of the electrode.

     In order to solve the above disadvantages, a method of solidifying by adding an organic curing agent to a solution electrolyte, a method of solidifying using a high molecular polymer, a method of producing a semi-solid DSSC by using a high viscosity ionic liquid, In addition, there is a technique for solidifying DSSC, such as a method of replacing organic HTM (hole transporting materials) as an electrolyte.

Solid polymer electrolytes mainly contain derivatives such as poly (ethylene oxide) (PEO), poly (propylene oxide) (PPO), ployphospazene and polysiloxane, but high molecular weight PEO has high crystallinity (~ 80%). This high crystallinity has disadvantages of low ion conductivity (˜S / cm) and diffusion coefficient at room temperature. Another method is to use a gel polymer electrolyte (semi-solid polymer electrolyte), which is a system composed of a polymer, an organic solvent, and a salt, in which an organic electrolyte is infiltrated into a solid polymer. In the gel polymer electrolyte, since the polymer forms a three-dimensional network by physical bonds through compound bonds or intermolecular interactions, the gel polymer electrolyte has a swelling body capable of retaining and retaining solvent molecules in the film. They are in the form of a solid film on the outside, but at the molecular level, the ionic conductivity value of the electrolyte solution permeated into the polymer is greater than or equal to ~ S / cm). However, the mechanical strength is weak, there is still a problem of sealing and there are many difficulties in applying to the role to role process.

    Another method is to use organic HTM (Hole transporting materials) electrolyte, and the materials used as HTM (Hole transporting materials) include triarylamines, polythiophene, PEDOT, PANI-DBSA, OMe-TAD. Triarylamines have high charge carrier mobility and are soluble at low temperatures. Polythiophene is thermally and environmentally stable and has the advantage of tuning solubility, electronic and electrochemical properties. But there is a pore filling problem. PEDOT shows high light transmittance and conductivity in the visible region and high stability at room temperature. PANI-DBSA has high conductivity but Voc and Jsc are lowered when it has high conductivity of S / cm or more. OMe-TAD has high conductivity but has the disadvantage of pore filling problem. The advantage of organic HTM is that it can be role to role process, is advantageous for large area and excellent in processability. However, it absorbs visible light and acts as a factor to reduce efficiency.

An object of the present invention is to provide a new type of solid electrolyte that can solve all the disadvantages of the electrolyte.

The present inventors have endeavored to solve the technical problem of the present invention and, as a result, have found that each component can be quantified at a time in a short time and have completed the present invention.

That is, the present invention adopts a new type of solid electrolyte containing both the structure of the conventional HTM type electrolyte and the polymer solid electrolyte, thereby providing a solid electrolyte for a solar cell having a very good performance that can solve the above problems. The present invention has been completed.

The present invention by inventing a new type of solid electrolyte prepared by grounding (grafted) HTL material on the side chain to a polymer compound having a copolymer of alkylene oxide-epiclohadrin having various composition ratios as a main chain, By replacing the electrolyte of the solar cell, to provide an electrolyte of excellent performance, and to provide a dye-sensitized solar cell using the same.

The polymer of formula (I), e.g., poly (ethylene oxide- co -epichlrohydrin) in HTM (Hole transporting material) by HTM (Hole transporting material) material through a copolymer form poly (ethylene oxide- containing material co - It is possible to increase the ionic conductivity by decreasing the crystallinity of epichlrohydrin) and increasing the amorphous region and increasing the mobility of the molecular chain in the amorphous region through the free volume.

      In addition, by using HTM of small molecular weight to suppress the Pore filling problem, which is a disadvantage of HTM, it is possible to penetrate to TiO2 interface and minimize the Pore filling problem.

     In addition, the effect of ionic conductivity is added by the transport of molecular chain and hole transporting by HTM (Hole transporting material) in Equation 1, resulting in higher ionic conductivity. -current) is increased to improve the optical conversion efficiency.

In addition, for example, ionic conductivity caused by the transport of molecular chains in poly (ethylene oxide- co- epichlrohydrin) is added to the effect of ionic conductivity caused by hole transporting by HTM (Hole transporting material) to realize higher ionic conductivity. Can be. Therefore, the open-circuit-voltage (Voc) and short-circuit-current (Jsc) of the dye-sensitized solar cell are increased to improve the light conversion conversion efficiency.

In addition, it is possible to realize the same high ionic conductivity in gel polymer electrolyte using LiI, KI, etc., and to reduce recombination in TiO2 interface and iodine electrolyte by HTM grounded to hydrophobic polymer chain. This branch is not only advantageous in large area, but also can realize high business feasibility through role-to-role process. Therefore, the open-circuit-voltage (Voc) and short-circuit-current (Jsc) of the dye-sensitized solar cell are increased to improve the light conversion conversion efficiency of the dye-sensitized solar cell.

This will be described in detail below.

The present invention relates to a solid electrolyte for solar cells having a structure such as the following formula (1).

(Formula 1)

(Wherein R1 is a C2-C8 straight or branched alkyl group, R2 is C1-C8 straight or branched alkyl group, R3 is C1, C2 or C3-C6 straight or branched alkyl group, X is O, NH group Where a and b represent the molar ratio and a + b = 1, a may be 0, where b is 1.

Examples of the material of Chemical Formula 1 will be described in detail using the following Chemical Scheme 1 as an example. After synthesizing Poly (ethylene oxide- co- epichlrohydrin) as shown in Chemical Scheme 2, nucleophilic substituents of compounds containing HTM (hole transfer material) structures were observed through nucleophilic substitution with chlorine of epicrolohydrin. The invention provides a new solid electrolyte containing the desired HTM.

                                    (Scheme 2)

Examples of the HTM material to be substituted in the polymer backbone are described in the following Chemical Formula 2, but are not limited to the HTM used in this field.

Claims (3)

A solid electrolyte for dye-sensitized solar cells using HTM having a structure of the following formula as a side chain of a polymer.

(Wherein R1 is a C2-C8 straight or branched alkyl group, R2 is C1-C8 straight or branched alkyl group, R3 is C1, C2 or C3-C6 straight or branched alkyl group, X is O, NH group Where a and b represent molar ratios and a + b = 1, a can be 0, where b is 1 and HTM means hole transport material.) The method of claim 1 R 1 and R 2 are —CH 2 CH 2 —, R 3 is —CH 2 — and X is O. The method according to claim 1 or 2,        The HTM is a solid electrolyte for a solar cell is obtained from a compound of the following formula.