Basic principles and structures of dye-sensitized solar cells

Basic principles and structures of dye-sensitized solar cells

Photosynthesis of green plants in nature is the most efficient solar energy conversion system known. Many people use organic photosensitizing dyes similar to chlorophyll molecular structure to design light energy conversion systems that artificially simulate photosynthesis, and conduct research on photoelectric conversion. Since organic photosensitizing dyes can be designed and synthesized by themselves, compared with inorganic semiconductor materials, there is a large choice of materials, and it is easy to achieve the goal of low cost. Metalloporphyrins and metal porphyrins are complexes composed of large conjugated organic molecules and metals, with high chemical stability and strong absorption in the visible spectrum. As organic photovoltaic materials, it is currently the object of extensive research. (High-quality Tycorun Battery is also available here for your choice)

Dye-sensitized solar cells (DSSCs) are a new type of solar cells developed based on nanotechnology in the past 20 years. Compared with traditional silicon cells, they are gradually favored by many researchers due to their low cost and high efficiency. The traditional DSSC is mainly composed of transparent conductive glass, porous titanium dioxide film, dye sensitizer, electrolyte solution (or solid electrolyte), counter electrode, etc. At present, the research on dye-sensitized solar cells mainly focuses on TiO2 thin film materials, the development of electrolytes and the design of dye molecules. How to improve the utilization of light, thereby improving the photoelectric conversion efficiency of DSSCs has always been a research hotspot in this field.

Since the sandwich structure used in traditional DSSC requires that the photoanode substrate must be transparent, transparent conductive glass (TCO) has become the best choice for traditional DSSC, which is also commonly used by researchers. It is formed by attaching a layer of oxides including In, Sb, Zn and Cd and their multi-component composite oxide film materials on the glass surface. The transparent conductive film is made of tin-doped oxide steel (In2O3: Sn, referred to as ITO) and fluorine The tin oxide (SnO2: F, referred to as FTO) is represented. After high temperature heat treatment of ITO, the surface resistance will increase by an order of magnitude, while the properties of FTO remain stable after heat treatment at this temperature, so FTO is often used as the base material of TiO2 film in traditional DSSC. . When selecting TCO conductive glass, the resistance and transmittance should be considered comprehensively. Generally, the greater the conductivity, the smaller the transmittance, and vice versa. The pursuit of low resistance and high light transmittance is an important direction in future TCO research.

Dye-Sensitized Solar Cell Light Energy Lantern
Dye-Sensitized Solar Cell Light Energy Lantern

The sunlight transmitted by the conductive glass will be absorbed by the dye, and the currently recognized better photosensitizing dye is the pinned bipyridine complex, and its basic chemical formula is ML2(X)2 (wherein, M represents ruthenium; L represents 4 , 4-Dicarboxy-2,2-bipyridine: X represents halogen, cyano, thiocyanate, acetylacetone, thiocarbamic acid, water, etc.). In this series of dyes, N3 (red dye) and N719 have the best performance and are the most widely used. The maximum absorption peaks of N3 are at 518nm and 380nm, and the corresponding molar extinction coefficients are 1.3×104L/(mol·cm) and 1.33×104L/(mol·cm), respectively. However, N3 and N719 have poor spectral response above 600 nm, and the absorption spectral range cannot be well matched with the solar spectrum. Therefore, this part of sunlight cannot be effectively utilized.

Designing a photosensitive dye system with better synthesis performance and further improving the light absorption in the long wavelength range is still one of the main research directions of people. Kubo et al. prepared a stacked dye-sensitized solar cell with N719 and black dye. It has good light absorption performance in the near-infrared, and can absorb sunlight with a threshold of less than 1000 nm, which makes up for the shortcoming of N719 dye’s poor light absorption ability in the long wavelength range, and can improve the spectral response range and photoelectric conversion efficiency of the cell. The layer-structured cells showed a 20% improvement in photocurrent compared to cells with N719 or black dye alone.

The development of dyes that absorb near-infrared and infrared wavelengths is also a focus of dye research. In recent years, amphiphilic dyes represented by Z907 and dye sensitizers with high absorption coefficient represented by K19 are the current research hotspots of polypyridine nail dyes.

Dye-sensitized solar cells, like amorphous silicon solar cells, are the main indoor application products due to their good low-light performance. They are not only used in windows (requires a certain light transmittance), but also in solar clocks and supermarket shelves. Display labels and calculators on the top and so on. These application objects do not require battery transparency, so this new improved structure still has many applications while improving battery efficiency.

Compared with traditional sandwich structure dye-sensitized solar cells, the new structural dye-sensitized solar cells have unique advantages in light utilization. By designing some new types of dye-sensitized solar cells, some new ideas can be provided for improving the efficiency of dye-sensitized solar cells in the future.

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