A potential way to improve the quality of Cu2ZnSnSe 4 absorber thin film by a one step process of sputtering using a single elementary target is proposed for thin film solar cells. As critical parameters, different S/Se ratios and grain boundary characteristics are achieved by adjusting sequential sulfurization and selenization post-treatment. The simple sulfurization of as-deposited film at 530 ° C in H2S is not effective in raising the performance but the additional Se annealing at a shorter duration of 5 min improves conversion efficiency from 0.12 to 3.21% with a drastic increase of the open circuit voltage. Positively-charged grain boundaries with narrow potential peaks seem to play a critical role for effective exciton separation and higher efficiency. The improvement is also understood as related to well-defined microstructures and the variable optical band gap.
Bibliographical noteFunding Information:
This work was financially supported by a grant of the National Research Foundation of Korea (2011-0020285).
© 2015 IOP Publishing Ltd.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics
- Acoustics and Ultrasonics
- Surfaces, Coatings and Films