ZJU scientists pioneer in developing a DSC with conversion efficiency of 10%
With energy crisis looming large, search for clean and sustainable energy has become a global issue. As the largest manufacturing and consumption country in solar cells, China is playing an increasingly important role.
Recently, the research team led by Prof. WANG Peng from ZJU's Department of Chemistry, and the research team led by Prof. Michael Grätzel in the Institute of Chemical Sciences & Engineering, École Polytechnique, engaged in collaborative research in stable and efficient dye-sensitized solar cell（DSC） and made remarkable achievements.
DSC is a low-cost solar cell belonging to the group of thin film solar cells. However，its outdoor applications have been limited by the problem on efficiency and long-term stability.
Plants and other organisms are dependent on photosynthesis to convert light energy into chemical energy that fuels the organisms’ activities. Termed as artificial photosynthesis， a DSC resembles an artificial leaf in structure， in which chlorophyll and a phosphate coating are replaced by a sensitizing agent and a porous semiconductor film.
WANG Peng et al. introduce a co-sensitized, ionic liquid electrolyte-based DSC meeting the requirements for high efficiency and long-term stability. A key feature of their embodiment is the concerted action of two judiciously designed organic dyes, whose co-adsorption at the surface of a mesoscopic TiO2 scaffold results in the formation of a compact and highly robust self-assembled monolayer, harvesting sunlight across the whole visible region and converting the photons into charges with near-unity quantum efficiency. Apart from producing a high photocurrent, the dense dye layer blocks the back electron transfer from TiO2 to the redox electrolyte, increasing the photovoltage. This allows for the development of a solar- to electric power-conversion efficiency of 10% with an ionic liquid-based DSC for the first time. Remarkably, the co-sensitized cell is stable under both full sunlight soaking at 60°C and heat stress at 85°C for 1,000 hr. These findings are published in a cover article entitled “Stable and Efficient Organic Dye-Sensitized Solar Cell Based on Ionic Liquid Electrolyte” in the journal of Joule.
DSCs have a wide spectrum of applications. When they are used as reflection glass curtainwalls, roofs or windows for a building, it will not only attain a self-sufficient supply of energy with no chemical pollution at a low cost, but it will become aesthetically appealing for its polychromous appearance. Moreover, DSCs can work for over 8 hours every day, far outperforming crystal silicon solar cells which can work for roughly 4 hours every day, thereby compensating the deficiency of relatively weak light emission.
This new type of solar cells has been industrialized. For example, the Science Tower in Graz, the second largest city in Austria, is installed with a 1,000 m2 translucent solar cell panel. The Swiss Tech Convention Center blends high-tech perfectly with magnificence with the decoration of colorful DSCs. “DSCs will dominate a larger market in the future. EU has proposed that the self-supply capacity of new buildings should take up 25% by 2025,” WANG Peng said.