| Name: | Description: | Size: | Format: | |
|---|---|---|---|---|
| 1.08 MB | Adobe PDF |
Advisor(s)
Abstract(s)
A dc magnetron sputtering-based method to grow high-quality Cu2ZnSnS4 (CZTS) thin films,
to be used as an absorber layer in solar cells, is being developed. This method combines dc
sputtering of metallic precursors with sulfurization in S vapour and with post-growth KCN
treatment for removal of possible undesired Cu2−xS phases. In this work, we report the results
of a study of the effects of changing the precursors’ deposition order on the final CZTS films’
morphological and structural properties. The effect of KCN treatment on the optical properties
was also analysed through diffuse reflectance measurements. Morphological, compositional
and structural analyses of the various stages of the growth have been performed using stylus
profilometry, SEM/EDS analysis, XRD and Raman Spectroscopy. Diffuse reflectance studies
have been done in order to estimate the band gap energy of the CZTS films. We tested two
different deposition orders for the copper precursor, namely Mo/Zn/Cu/Sn and
Mo/Zn/Sn/Cu. The stylus profilometry analysis shows high average surface roughness in the
ranges 300–550 nm and 230–250 nm before and after KCN treatment, respectively. All XRD
spectra show preferential growth orientation along (1 1 2) at 28.45◦. Raman spectroscopy
shows main peaks at 338 cm−1 and 287 cm−1 which are attributed to Cu2ZnSnS4. These
measurements also confirm the effectiveness of KCN treatment in removing Cu2−xS phases.
From the analysis of the diffuse reflectance measurements the band gap energy for both
precursors’ sequences is estimated to be close to 1.43 eV. The KCN-treated films show a better
defined absorption edge; however, the band gap values are not significantly affected. Hot point
probe measurements confirmed that CZTS had p-type semiconductor behaviour and C–V
analysis was used to estimate the majority carrier density giving a value of 3.3 × 1018 cm−3.
Description
Keywords
Citation
Publisher
IOP Science