Growth Conditions and Structural Properties of Cu(In,Ga)Se2 Thin Films Prepared by Selenization Method Using Diethylselenide

Abstract

The relationship between the selenization conditions and structural properties of Cu(In,Ga)Se2 (CIGS) thin films was investigated for the selenization method using diethylselenide (DESe). The grain structure changed markedly depending on selenization temperature, selenization time, and DESe flow rate. The CIGS thin films selenized at a high temperature (HT: 500–540 °C), which is referred to as a one-step selenization are very rough. On the other hand, the films selenized at a low temperature (LT: 350–450 °C) exhibited a relatively uniform thickness and densely packed grains, although they contain second binary phases such as In–Se and Cu9Ga4. To form a single-phase chalcopyrite CIGS film, a two-step selenization method is examined, in which the films selenized at LT (first step) are subsequently selenized at HT (second step). Single-phase densely packed CIGS thin films with uniform thickness were obtained by the two-step selenization. The use of the InSe/Cu0.7Ga0.3 precursor was proposed, and the selenization of this precursor successfully yielded single-phase CIGS thin films with a flat surface. The importance of the role of InSe during the selenization process using DESe is discussed.