Solar Server Interview with Sylvia Tulloch, Managing Director of Dyesol

Sylvia Tulloch
Sylvia Tulloch

Materials scientist Sylvia Tulloch is co author of several Dyesol patents. In the Solar server Interview she answers Questions regarding the progress and state of nano crystalline Solar Cells based on a concept analogous to chlorophyll absorbing light and thus generating electrons which enter the conduction band of a high surface area semiconductor film and further move through an external circuit, thus converting light into "green" power.

Solar Server: Mrs. Tulloch, your company Dyesol wants to commercialise the Dye Solar Cells. What kind of technology is that?

Sylvia Tulloch: Dye solar cells are 3rd generation PV (photovoltaics). To be clear, for 1st generation the semiconductor is crystalline silicon wafers sliced from an ingot. 2nd generation is thin film semiconductor, initially amorphous silicon deposited from a gaseous phase, and subsequently other semiconductors such as CIGS (copper indium gallium selinide). 3rd generation is bimimic that is it mimics the natural process of photosynthesis, where the green dye chlorophyll in a leaf absorbs the energy from light, and generates electrons which are captured in the nanostructured leaf tissue. In DSC, the leaf tissue is replaced by a nano particles of titania (which is the white pigment in paint and tooth paste).

Solar Server: The nano crystalline Dye Solar Cells named "Grätzel-Cell" by its inventor have been developing since the early nineties of the last century. Which problems has to been solved and which progresses have been achieved?

Sylvia Tulloch: Early problems now solved include:

- Chlorophyll is not a very stable dye (remember a leaf is only green for a few months), so dyes which were stable for decades had to be developed.
- The DSC is an electrochemical cell (more like a battery than other solar cells). This means that an electrolyte is necessary, and the first, and still the most efficient electrolytes were liquid, so cell and module designs which prevented electrolyte leakage had to be developed.

Today, with these two problems solved, work is centred mostly on either:
- Getting higher efficiency (it is the aim of all solar cell researchers to raise efficiency, whether 1st, 2nd or 3rd generation.
- Developing designs for specialised applications, such as BIPV or integration into electronic equipment.
- Methods for volume manufacture, automation etc.

Solar Server: The effectiveness of the Dye Solar Cells is nor clearly under the effectiveness of the "classic" silicium module, which have more or less 90 % of the market. Is it possible that the effectiveness of your new technology can be as good as the effectiveness of the silicium-technology?

Sylvia Tulloch: DSC has efficiency more like amorphous silicon than crystalline "classic" silicon, but the real aim is not efficiency as such, but the cost of electricity produced by the modules. DSC has the advantage of working much more effectively in non optimum light as in haze, in shadows, at unusual angles, and under indoor lighting.

Solar Server: One last Question: When will commercial Dye Solar Cells be available on the market and what may be the price?

Sylvia Tulloch: Our customer G24i has announced that they will be selling DSC solar modules within one year, and we expect other corporations to follow. Dyesol is not in control of the pricing of DSC panels, but personally, I believe that pricing of solar panels in the future will not be closely technology linked, but rather be set by, what the market is prepared to pay for solar electricity.

Solar Server: Thank you very much for this Information, Ms. Tulloch.

Sylvia Tulloch will be present at the trade fair "nanoeurope" on September 11th –13th at St. Gallen (Switzerland)