Significant advancement in dye-sensitized solar cells achieved

Researchers in South Korea have suggested a new approach to creating cost-effective and more efficient dye-sensitized solar cells, which will mean significant advancement in the thin-film market.

So far in the development of this thin-film technique, researchers have faced one major setback; the efficiency of the cells has been half that of the more commonly used silicon-based cells. However, this new approach will improve the power consumption rates of dye-sensitized solar cells by at least 50%.

Park Nam-gyu, a researcher from the Korea Institute of Science and Technology (KIST), said his team has discovered a breakthrough method, which enables a sequential bonding of dyes in the thin, titanium dioxide (TiO₂) layers used in dye-sensitized solar cells.

Park said, ''In the existing prototypes, the TiO₂ films bond with just one kind of dye, and developing techniques to allow the films to absorb dyes of different colours, thus allowing the solar cell to absorb and use a broader spectrum of daylight, has been a key issue.''

''We were the first to achieve this by developing materials in both the mobile and stationary phase that enables the selective position of dye molecules with different absorption ranges. This could significantly improve power conversion rates that currently max at 11%.''

Once commercialization of these cells has been achieved one should expect a huge shift in the solar market, as these dye-sensitized cells will be of the same efficiency as silicon-based cells, yet they will be far more cost-effective and much simpler to manufacture.

Although this is a major advancement in the solar field, it is of course still at a developmental stage, as many different prototypes are being made in order to find out which has the preferred specifications.

The basic design of these dye-sensitized solar cells is based on a semiconductor formed between a photosensitized anode and an electrolyte. The cells are made of a porous film of tiny, nanometer-sized TiO₂ particles, which are covered with a layer of dye that is in contact with the electrolyte.

When contacted by sunlight, the dye injects a negative charge in the nano-particles and a positive charge into the electrolyte, thus converting the light into electrical energy.

The positioning of the dye molecules is critical in boosting power conversion rates, as it enables different absorption ranges in the TiO₂ films. To achieve this, Park's team mimicked the concept of the ''stationary phase'' and ''mobile phase'' in chromatography that is a scientific method that involves separating individual chemical compounds from mixtures. Involved in this process are two phases, the stationary phase and the mobile phase. These phases are fairly self-explanatory, however it is important to mention that the mobile phase involves moving in a definite direction.

Park's team adopted the method of column chromatography, which involves a separation technique in which the stationary bed is a tube. The solid particles of the stationary phase fill the inside wall of the tube, leaving an uninterrupted path in the middle for the gas and liquid of the mobile phase.

In using the method to improve dye-sensitized solar cells, Park's team used the porous TiO₂ film, filled with polystyrene, as a stationary phase, while developing a Bronsted-based-containing polymer as a mobile phase. By controlling the release and accumulation of the substances, the researchers managed to vertically align yellow, red and green dyes within the TiO₂ film, which was confirmed by an electron probe micro-analyzer.