Recrystallization of CIGSe layers grown by three-step processes: A model based on grain boundary migration

The present paper aims at stating when and why small grains transform to large grains during Cu(In,Ga)Se2 (CIGSe) film growth following three-step processes. Experimental observations revealed that such recrystallization is achieved when the nominal composition of the films is close to a 1:1:2 stoichiometry. A new model based on grain boundary migration theory is proposed in order to establish a causal relationship between such a composition threshold and grain boundary motion yielding large grain formation. This model is related to some of the experimental observations related to CIGSe layer growth that have previously been difficult to explain.