Martin Green, professor at the University of New South Wales (UNSW) in Australia showed how the efficiencies of crystalline silicon (Si) photovoltaic (PV) cells will be improved at EU PVSEC, an international conference on PV cells.
Green is the person who achieved the world's highest efficiency of a crystalline Si PV cell (cell conversion efficiency: 25%).
Green introduced a method of forming a layer of a different material on Si to form a tandem structure. The title of his lecture was "Silicon Wafer-Based Tandem Cells: The Ultimate Photovoltaic Solution?"
When only Si is used, the maximum cell conversion efficiency is 29%. But when a layer of another material is formed on Si, it increases to 42.5%. And when yet another material is placed on it, the efficiency becomes 47.5%, he said.
As candidate materials, Green referred to (1) group III-V materials including GaAs, which is for space use and light-harvesting systems, (2) CZTS, which is used for compound semiconductor thin-film PV cells that do not use indium (In) and (3) material having a perovskite structure, which is drawing attention as a material for dye-sensitized PV cells.
Though he did not show any research results, he said that each of the candidate materials has advantages and disadvantages in terms of conversion efficiency, cost, etc.
An engineer who is working for a PV cell maker and attended the conference said, "We are considering the same thing as one of the methods for going beyond the limits of silicon."