Dye Sensitizers For Solar Energy

In dye-sensitized solar cells (DSSCs), dye sensitizers function to capture solar photons. Whether the dye sensitizer can absorb sunlight to the maximum extent directly determines the maximum energy conversion efficiency that the photovoltaic cell can obtain. An ideal dye sensitizer should have high light-harvesting ability, broad absorption spectrum, good photostability and long excited state lifetime. In order to obtain a high-efficiency dye sensitizer, the molecular structure design of the dye should follow the following principles: (1) the absorption spectrum of the dye should cover the ultraviolet-visible region and the near-infrared region; (2) the lowest unoccupied orbital energy level (LUMO) of the dye cannot be lower than the conduction band energy level of TiO2 to facilitate electron injection; (3) the oxidation state and excited state stability of the dye molecule must be high; (4) the dye molecule should have polar groups such as carboxyl and hydroxyl groups, which can be tightly attached to TiO2. Dye sensitizers can be divided into two categories: metal complexes and metal-free organic sensitizers. For metal complexes, the common ones are ruthenium (Ru) complexes and porphyrin zinc (Zn) complexes. For metal-free organic compounds, triphenylamines, indoles and coumarins are common. Among them, ruthenium (Ru) complex dye sensitizers have good thermal stability, chemical stability and photoelectric conversion efficiency, and are currently one of the most widely used dye sensitizers.

Molecular structures of some dye sensitizersFigure 1. Molecular structures of some dye sensitizers

Applications:

  • DSSC: DSSC has been widely used because of its advantages of simple process, low cost and low pollution. The choice of dye sensitizer has a great influence on the performance of DSSC. Rational selection and structural design of dye sensitizers are prerequisites for the development of high-efficiency DSSCs. Each type of dye sensitizer has advantages and disadvantages. The development of efficient DSSC devices requires the use of dye sensitizers with large spectral response range, high electron injection efficiency, light resistance, and high chemical and thermal stability. Ruthenium (Ru) complexes and porphyrin zinc (Zn) complexes have the advantages of strong absorption in the visible light region, high chemical stability, and long life. Triphenylamines and indoles have strong electron donating ability and excellent photoelectrochemical properties. For different DSSC application fields, choosing different dye sensitizers for performance regulation can promote the wider application of DSSC.

Reference

  1. Neeraj Tomar, Anupam Agrawal, Vijaypal Singh Dhaka, Praveen K. Surolia. Ruthenium complexes based dye sensitized solar cells: Fundamentals and research trends [J]. Sol. Energy, 2020, 207, 59-76.
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