Novel back contact silicon solar cells designed for very high efficiencies and low-cost mass production

To make photovoltaics an economic source of energy the efficiency of industrial crystalline silicon solar cells has to be drastically increased without complicating the fabrication process. Solar cells with both contacts on the rear side are promising candidates for further increasing cell and module efficiency as well as significantly simplifying module assembly. A new generation of back contact silicon solar cells, based on the self-aligned mask and photolithography-free oblique-evaporation-of-contact (OECO) technology is introduced. The outstanding high-efficiency features and the low-cost production features including the advantages for thin wafers and bifacial operation of the so called BACK-OECO solar cells are outlined. Simulation studies based on the experimental experience with front-contacted OECO cells are revealing that these new devices have the potential to achieve efficiencies up to 22% under industrial conditions using Cz grown silicon. Custom-made high-throughput processing equipment recently completed by us for the crucial fabrication steps including back surface grooving, oblique metal evaporation and high quality low temperature surface passivation is described.