| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 78246 | Solar Energy Materials and Solar Cells | 2013 | 9 Pages |
Author-Highlights•Study of the effects of the sulphurization time on CZTS thin films.•Residual presence of metallic phases was detected for longer sulphurization times.•Absorber layer increasing conductivity activation energy was observed for longer sulphurization time.•Impedance measurements allowed the estimation of the devices' electrical properties.
We report the results of a study of the sulphurization time effects on Cu2ZnSnS4 absorbers and thin film solar cells prepared from dc-sputtered stacked metallic precursors. Three different time intervals, 10 min, 30 min and 60 min, at maximum sulphurization temperature were considered. The effects of this parameter' change were studied both on the absorber layer properties and on the final solar cell performance. The composition, structure, morphology and thicknesses of the CZTS layers were analyzed. The electrical characterization of the absorber layer was carried out by measuring the transversal electrical resistance of the samples as a function of temperature. This study shows an increase of the conductivity activation energy from 10 meV to 54 meV for increasing sulphurization time from 10 min to 60 min. The solar cells were built with the following structure: SLG/Mo/CZTS/CdS/i-ZnO/ZnO:Al/Ni:Al grid. Several ac response equivalent circuit models were tested to fit impedance measurements. The best results were used to extract the device series and shunt resistances and capacitances. Absorber layer's electronic properties were also determined using the Mott–Schottky method. The results show a decrease of the average acceptor doping density and built-in voltage, from 2.0×1017 cm−3 to 6.5×1015 cm−3 and from 0.71 V to 0.51 V, respectively, with increasing sulphurization time. These results also show an increase of the depletion region width from approximately 90 nm–250 nm.
