Preparation of high-quality SnS thin films for self-powered photodetectors and solar cells using a low-temperature powder technique

Abstract

The binary compound tin-sulfide (SnS) is a promising absorber semiconductor for visible photodetectors and solar cells due to its optimum forbidden band gap and high absorption coefficient. It was shown in this study that high quality SnS powder can be prepared by a powder preparation method at relatively low temperatures. The resulting powder was used to deposit SnS layers via thermal evaporation. The SnS layers were then grown on molybdenum coated and uncoated glass substrates. The crystalline structures of the films prepared on molybdenum coated substrates were reported to be enhanced. According to the XRD and Raman measurements, the thin films grown on both substrates did not contain foreign phases such as SnS2 and Sn2S3. The optical investigation of samples revealed a high absorption coefficient that exceeded ∼8 × 104 cm−1 at 700 nm wavelength. Furthermore, the optical and electrical measurements show that SnS thin films exhibit p-type conductivity and can be employed in heterojunction solar cells and self-powered photodetectors with a desired forbidden band gap of ∼1.5 eV. A short circuit current density of ∼1.5 mA/cm2, an open circuit voltage of ∼113 mV, and an efficiency of 0.05% were obtained for the Ag/SnS/CdS/ITO/glass structured solar cell. The on/off current ratio of the prepared self-powered Ag/SnS/CdS/ITO/glass structured photodetector was as high as 28316.76 ± 1588 at zero bias. On the other hand, it was shown that the detectivity of the self-powered photodetector device can be tuned between (1.201 ± 0.011)x108 and (1157.83 ± 2.39)x108 Jones by adjusting the substrate temperature. A responsivity value as high as (15149.47 ± 31.31) μA/W has been achieved at zero bias.