Berlin 2015 – scientific programme

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DS: Fachverband Dünne Schichten

DS 36: Poster Session I

DS 36.2: Poster

Thursday, March 19, 2015, 09:30–12:00, Poster A

Reflectometry as a non-destructive tool for CZTS-synthesis control — •Stephan van Duren, Sergiu Levcenco, Justus Just, and Thomas Unold — Helmholtz-Zentrum Berlin, Hahn-Meitner-Platz 1, 14109 Berlin

Kesterite (Cu2ZnSnS4 or CZTS) is an attractive non-toxic, earth abundant material for thin film solar cells. Current challenges are absorber homogeneity and reproducibility. In this study, reflectometry has been used to gain better understanding of the secondary phases, impure absorbers and its potential for in-situ process control. Ex-situ reflection measurements were performed on CuS, ZnS and CZTS absorbers with different composition. An in-situ reflection setup has been designed and built to be used in conjunction with a vacuum chamber. Temperature dependent reflection measurements were carried out to study CuS and ZnS in a range from 25°C to 550 °C. A characteristic dip in the reflection spectrum around 620 nm of CuS was identified, also during thermal treatment. A structural change of the CuS to Cu2-xS could be deduced from the irreversible change of the reflection spectrum during annealing to 550°C. For a ZnS thin film, a phase shift and reduction of the interference pattern amplitude was observed across the full spectral range (UV-VIS-NIR) after annealing at 500°C. From comparison with XRD measurements of samples before and after annealing we attribute these changes to an improved crystallinity of the layer and changes in the optical constants. Experimental results have been compared with several simulated configurations such as ZnS/CZTS/Mo, CuS/CZTS/Mo and CZTS/Mo.