Effect of substrate and selenization temperature on the properties of RF sputtered CZTSe layer

Abstract

Cu2ZnSnSe4 (CZTSe) thin films were deposited by RF sputtering method at different substrate temperatures, followed by an annealing step in SnSe2. It was found that the substrate temperature significantly affected phase structure and surface morphology of the precursor films. The annealed films show better crystallinity than the precursors. Single kesterite CZTSe phase was observed when the annealing temperature was below 505 °C. No photoconductive response was observed for precursor film, whereas the annealed films showed obvious photo-response under illumination. The film annealed at 480 °C shows the best photoconductivity, as a result of low carrier concentration (8.2 × 1014 cm−3) and high mobility (26.4 cm2·v−1·s−1). The Mo/CZTSe (annealed at 480 °C)/CdS/Au diode shows obvious rectification character. By using optimized CZTSe film, CZTSe solar cell was fabricated, and it showed power conversion efficiency of 0.34% with relatively high open circuit voltage of 350 mV. This work provides a way to modulate the structure and property of CZTSe film deposited by sputtering technique for fabricating solar cells.