Impact of pre-annealing temperature on the formation of Cu2ZnSnS4 absorber layer

Annealing is one of the major parameters influencing the properties of CZTS (Cu2ZnSnS4) thin films. The temperature dependence of structural, optical, electrical and compositional properties of CZTS thin films has been presented here. A simple non vacuum based method was used for the fabrication of CZTS thin films. Basically, the fabrication process consists of four steps: 1) wet ball milling of pure elemental powders; 2) preparation of a paste in an agate mortar; 3) deposition of the films using the doctor's blade method; 4) two-stage annealing treatment of the films in an inert atmosphere. The two-stage annealing cycle comprises a heating ramp up to 200 degrees C or 300 degrees C, holding at these temperatures for 30 min, followed by another heating ramp up to 450 degrees C or 500 degrees C and holding at these temperatures for 30 min. The processed materials are characterized in terms of their structure, morphology and composition. Optical and electrical properties were also evaluated. The main result is that the first stage annealing temperature has a strong influence in the final properties of the CZTS thin films. (C) 2015 Elsevier B.V. All rights reserved.