The use of nano-scale semiconductor materials such as TiO2, ZnO, and SnO2 as the photoelectrodes of solar cells is a worldwide research hotspot. Among them, nano-TiO2 has become the most commonly used material for the study of photovoltaic solar energy conversion cells due to light stability and non-toxicity.
Research progress
In 1991, Brian O Regan and Graetzel M of the Lausanne Institute of Technology in Switzerland reported a new type of high-efficiency solar cell using a dye-sensitized TiO2 nanocrystalline film as a photoanolyst, thus creating a new era of solar cells, the first in the world. Nano solar cells were born.
However, there are many defects that cannot be improved in the use of liquid electrolytes as hole transport materials. For example, due to the complicated sealing process, leakage of electrolyte is caused by long-term placement, there is a reaction between the sealant and the electrolyte in the battery, and the electrode has a phenomenon of light corrosion. Sensitized dyes are easy to desorption, and researchers have made solid-state nano-crystalline solar cells instead of solid-state hole-transport materials and have made gratifying achievements.
In 1996, Masamitsu et al. used solid polymer electrolytes to prepare all-solid-state solar cells. Using a special preparation method, a highly ion-conducting electrolyte was obtained, continuous photocurrent was obtained, and photoelectric conversion efficiency of 0.49% was obtained.
In 1998, Graetzel et al. used OMeTAD as the hole transport material to obtain a photoelectric conversion efficiency of 0.74%, and the monochromatic light photoelectric conversion efficiency reached 33%, which attracted the attention of the world, and made the nano-crystalline solar cell move toward the solid state. A big step.
One of the international research hotspots is to connect a single liquid junction TiO2 nano solar cell in series to increase the open circuit voltage. The Institute of Plasma Physics of the Chinese Academy of Sciences has made major breakthroughs in this field for research projects undertaken by the main undertaking units. In mid-October 2004, a small-scale demonstration power station with a capacity of 500 watts was built, and the photoelectric conversion efficiency reached 5%. This achievement has made China's large-area area of ​​dye-sensitized nano-crystalline thin-film solar cells at the leading position in the world, laying a solid foundation for further promoting the practical application of low-cost solar cells in China.
Expertise
Domestic and foreign patents have been disclosed in some related fields, of which Japan has the largest number of patents. Here is a brief introduction of some patents in recent years.
The CN1350334 nanocrystalline solar cell electrode disclosed in Beijing University on May 22, 2002 and its preparation method relate to a nanocrystalline solar cell electrode and a preparation method thereof, and uses a wide bandgap semiconductor nanocrystalline film as a substrate on the substrate. A layer of metal ions is adsorbed on the surface, and a photosensitizer is adsorbed on the metal ion adsorption layer. The surface modification of metal ions improves the photoelectric conversion performance of the electrodes and improves the photoelectric conversion efficiency of the solar cells. Compared with pure TiO2, the photoelectric conversion efficiency of the metal ion-modified TiO2 nanocrystalline solar cell is improved by 5 to 14%, and can be widely used as an electrode in the solar energy field.
Southeast University on January 12, 2005 disclosed CN1564326 soft-based solid-state dye-sensitized thin-film solar cells and a preparation method thereof. The soft-base solid-state dye-sensitized thin-film solar cell is a soft-based solar cell with low cost, simple manufacturing process, stable performance, and theoretically the lifetime can reach more than 20 years. The structure of the solar cell is a layered structure, namely: A TiO2 nanocrystalline film is disposed under the photoconductive polyester sheet, a LnPc2 sensitized layer is disposed under the TiO2 nanocrystalline film, a solid electrolyte layer is disposed under the LnPc2 sensitized layer, and a flexible metal film back electrode is disposed under the solid electrolyte layer. A high-barrier composite Al film is provided under the flexible metal film back electrode.
CN1645632, a solid dye-sensitized nanocrystalline film solar cell and a preparation method thereof, are specifically disclosed in Fudan University, published on July 27, 2005, which is specifically a dye sensitization formed by hydrogen bonding interaction between an ionic liquid and an inorganic nanoparticle. A solar cell having a solid electrolyte as an electrolyte material assembled on the surface of the nanocrystal and a preparation method thereof. In the solar cell, a solid electrolyte is assembled on the surface of a wide bandgap semiconductor nanocrystal film that adsorbs a photosensitizer instead of a liquid electrolyte, thereby solving the problem of encapsulation of the liquid electrolyte, and without significantly reducing the photoelectric conversion efficiency of the battery, Can significantly extend the life of dye solar cells. The wide bandgap semiconductor nanocrystalline film is a TiO2 nanocrystalline film.
The Institute of Plasma Physics, Chinese Academy of Sciences applied for several patents on dye-sensitized nano-film solar cells. Among them, three invention patents issued on September 24, 2003 related to electrolyte solutions and electrodes for dye-sensitized nano-film solar cells. Preparation method, sealing method and the like, CN 1444290 discloses an electrolyte solution for a dye-sensitized nano-diaphragm solar cell, with A, B or B, F or A, B, and F as the main components, and the other four compounds are compounded or not compounded. One or several components of the component make up the electrolyte solution, in which component A - organic solvent or mixed organic solvent; B component - good electrochemically reversible I2/I - i.e. I3-/I-? redox Electron pairs; C component - photoanode complexing agent; D component - iodide cation complexing agent; E component - I2 compounding agent; F component - ionic liquid; G component - UV absorber. This electrolyte solution has high electrical conductivity, low viscosity, good electrochemical reversibility, good low temperature stability, strong UV resistance, can increase solar cell efficiency, increase solar cell life, and its own performance Stability, no pollution to the environment and other advantages.
Institute of Plasma Physics, Chinese Academy of Sciences CN2724205, a large-area internal parallel dye-sensitized nanocrystalline thin film solar cell disclosed on September 7, 2005, includes a transparent substrate on both upper and lower sides, a transparent conductive film on the transparent substrate, and a transparent conductive film The conductive electrode and the catalyst layer are arranged at intervals, the conductive electrode on the other transparent conductive film and the nanoporous semiconductor material block are arranged at intervals, and the nanoporous semiconductor material is impregnated with the dye. The two transparent substrates are stacked together, the periphery is sealed into a cavity, and the cavity contains electrolyte. The utility model creates internal parallel electrodes of the battery and obtains the required output current of the solar battery. The battery seal function is good, ensuring the long-term stability of the battery operation. The technology and method of the utility model are simple and easy to operate, low in price and stable in battery performance.
Japan SEIKO EPSON CORP on Apr. 27, 2001 disclosed JP2001119052 semiconductor and solar cell and its preparation method. Traditional wet solar cells contain dyes in titanium oxide electrodes, which are very sensitive to absorption wavelengths, but because TiO2 decomposes these organic dyes, its lifetime does not meet practical requirements. This patent solves this problem by sintering anatase TiO2 particles into a porous TiO2 semiconductor, which also contains impurities such as chromium or vanadium.
Japan Kaneko MASAHARU on June 24, 2003 disclosed a method for preparing a dye-sensitized solar cell and a TiO2 film and an electrode, and provided a spray decomposition method for preparing a porous TiO2 film, and the utility and productivity were guaranteed. Thin film solar cell electrodes can increase the solar cell energy conversion rate. The specific method is to add a titanium mixture to a TiO2 sol solution to obtain a raw material solution, or to mix an amorphous TiO2 sol solution and an anatase TiO2 sol aqueous solution to obtain another raw material solution. The two raw material solutions were sprayed intermittently onto the substrate, the titanium mixture was thermally decomposed at high temperature, and a TiO2 porous film was formed on the substrate. A dense TiO2 buffer film was prepared using a mixture of organic titanium as raw material between the transparent electrode and the TiO2 porous film.
The Greek LIANOS PANAGIOTIS on November 4, 2004 disclosed WO2004095481, an electrochemical solar cell made of a nanostructured organic-inorganic material, and describes a structure of a solid-state photoelectrochemical solar cell, including a thin film of a nano organic-inorganic material that can convert solar energy. Convert to electrical energy. The main components of the battery include: (1) commercial transparent conductive glass; (2) a transparent TiO2 film, an organic metal mixture of germanium as a photosensitizer; (3) a solid gel electrolyte layer prepared from a nanostructured organic-inorganic material (4) As a commercial conductive glass anode, a layer of platinum can be deposited.
Application prospect
Nano-TiO2 solar cells have a high photoelectric conversion rate comparable to that of conventional solid-state photovoltaic cells, and the low price makes this battery have a broad prospect and potential commercial value. Although there are still some problems with such solar cells, further research is needed. However, nano solar cells challenge the future with its huge advantages of high efficiency, low price, and no pollution. We believe that with the advancement of science and technology and the advancement of research, this solar cell will have a vast application prospect.
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