Scientists belonging to EPFL’s Institute of Microengineering in Neuchatel showcased "hybrid" photovoltaic cells with a record 21.4% energy conversion efficiency at the European Photovoltaic Solar Energy Conference and Exhibition in Frankfurt.
High-efficiency heterojunction solar cell. © IMT / EPFL
The achieved efficiency is a new record and will help reduce the cost of solar cell based installations. The research was presented by the director of the Photovoltaics Laboratory (PVlab), Prof. Christophe Ballif and his team. The PVlab performs studies in thin film solar cells and heterojunction technologies which are also called as "hybrid" technologies. This technology will help improve the efficiency of solar cells. It involves application of an amorphous silicon layers on the two sides of a crystalline silicon wafer. The amorphous silicon layer is just 1/100th of a micron thick. The application on both sides is considered as a sandwich concept which enhances the effectiveness of the PV sensors.
Two types of silicon are involved and in order to ensure the efficiency of their assembly, their interface has to be optimized. Researchers selected "p-doped silicon," which is considered to be the most cost-effective and common crystalline cell. They optimized the amorphous silicon layer application and achieved a conversion efficiency of 21.4%. This is much higher than the typical 18% -19% efficiency that has been achieved so far. The open-circuit voltage measured was 726 mV, which is considered as another achievement.
The commercialization process has been commenced by Meyer Burger. The production cost of these sensors is expected to reach 100 francs/m2 within a couple of years and the surface will be able to generate 200 - 300 kWh annually. The research suggests that an investment of 2000 francs would be enough for providing power for a household with four inhabitants.
The study is to be published in the IEEE Journals of Photovoltaics.