Method for backside surface passivation of solar cells and solar cells with such passivation

摘要

The present invention provides a method for dielectric passivating the surface of a solar cell by accumulation of negative fixed charges of a first type at the interface between semiconductor material and a passivating material. According to the invention the passivating material comprises an oxide system, for example a binary oxide system, comprising Al2O3 and at least one metal oxide or metalloid oxide which enhances the tetrahedral structure of Al2O3, e.g. an (Al2O3)x(TiO2)1-x alloy. In this way it is possible to combine the desirable properties from at least two different oxides, while eliminating the undesirable properties of each individual material. The oxide system may be deposited onto the semiconductor surface by means of a sol-gel method, comprising the steps of formation of the metal oxide and/or metalloid oxide sol and the aluminium solution and then carefully mixing these together under stirring and ultrasonic treatment. Thin films of the oxide system may then be deposited onto the semiconductor surface by means of spin coating followed by a temperature treatment.