A method to improve crystal quality of CZTSSe absorber layer

In this work, a fabrication process of high crystallinity CZTSSe absorber layer is presented. The CZTS structure is firstly prepared by spin-coating method then the film is converted into CZTSSe via selenization process using graphite box and tube furnace. Se powder has been used as source of selenizing vapors. By keeping the annealing temperature as constant and changing the mass of Se powder, the structural, optical, electrical properties, and composition of CZTSSe thin films are investigated. With substitution of S by Se, the smoothly, densely packed morphology and large grain size have been achieved. At optimal Se mass, the p-type CZTSSe film has bandgap energy, hole concentration, and resistivity of 1.27 eV, 1.7 × 10 19 cm −3 and 0.57 Ω.cm respectively which are suitable for photovoltaic application. To prepare the high crystalline structure CZTSSe absorber layers, we adopted the two-step process, CZTS thin films were prepared by a non-toxic, simple and economical spin-coating technique and then the films were converted into CZTSSe films by selenization in a tubular quartz furnace. In selenization step, CZTS thin films and selenium powder were loaded into a graphite box and inserted into the furnace. The influence of the Se powder content in selenization process on the crystal growth, optical, electrical properties, and surface morphology of CZTSSe thin films is investigated. Highlights High crystallinity CZTSSe absorber layer are successfully prepared by spin-coating method on glass substrates and selenization process using Se powder. The influence of the Se powder content in selenization process on the crystal growth, optical, electrical properties, and surface morphology of CZTSSe thin films is investigated. At optimal Se amount of 0.02 g, the p-type CZTSSe film had bandgap energy, hole concentration and resistivity of 1.27 eV, 1.7 × 1019 cm-3 and 0.57 Ω cm respectively which were suitable for photovoltaic application.