Structural, optical and electrical properties of evaporated kesterite films with different off-stoichiometric type

Kesterite thin films with four different off-stoichiometry have been synthetized by sequential evaporation of ternary (Cu2SnS3 or Cu3SnS4) and binary (ZnS) layers, following sulfurization (with elemental S) at 450 degrees C or 500 C. Zn-poor compositions (Zn/Sn < 1.0) are used to study the effect of substitutional Sn-Zn defects, together with V-Zn defects when Cu/Sn similar to 2.0 (sample CZTS1) or with Cu-Zn defects for Cu/Sn > 2.0 (sample CZTS2). Besides, the effect of cationic disorder is also studied for Zn/Sn similar to 1.0, producing Zn-Cu and Sn-Cu defects when Cu/Sn similar to 2.0 (sample CZTS3) or Cu-Zn and Cu-Sn for Cu/Sn > 2.0 (sample CZTS4). The crystalline structure, morphology, optical and electrical properties of the different samples have been analyzed comparatively by X-ray diffraction (XRD), scanning electron microscopy (SEM), spectrophotometry and coplanar electrical measurements. The highest crystallinity was achieved by the reaction of Cu3Sn4 and ZnS (sample CZTS4) at 450 degrees C, with a wide bandgap and low resistivity, which remain unchanged when increasing the heating temperature to 500 degrees C.

Automated summary

By synthesizing kesterite thin films with different off-stoichiometry, the effects of substitutional defects and cationic disorder on the crystalline structure and properties were studied.