Laser induced crystallization: a method for preparing silicon thin film solar cells

The preparation of coarse grained silicon thin films on glass suited for solar cells is investigated. The authors start from amorphous hydrogenated silicon thin films several 100 nm thick deposited on glass. Different laser crystallization processes are discussed. By an Ar⁺ laser scan, the amorphous layer is melted and recrystallized to grains several 10 μm in size. Alternatively an explosive crystallization process was applied in which the film is preheated to 1000°C by an Ar⁺ laser. The explosive crystallization is induced by an additional Nd:YAG laser pulse. In this process, at any position, the melt exists only for some ns. Grains of several μm in length were produced. The films were thickened to several μm by simultaneous deposition of further a-Si:H and in situ epitactic crystallization applying repeated excimer laser pulses