Annealing temperature of nanostructured SnS on the role of the absorber layer

Abstract

This study reports an experimental and theoretical research on the optimal annealing temperature, absorber layer thickness, and operational temperature of nanostructured SnS-based solar cells fabricated using the ethyl cellulose binder. The SnS powder was synthesized by a co-precipitation method. Characterization of the prepared powder by X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) revealed polycrystalline orthorhombic nanostructures with a mean size lower than 50 nm while UV–Vis-NIR and photoluminescence (PL) spectroscopies showed the suitability of the nanostructures for photovoltaic applications. According to the initial assessments, the SnS nanostructures were used to fabricate solar cell devices by depositing a blocking layer (BL) and an electron transport layer (ETL), as the buffer layers, and annealing the absorber SnS layer at 200–500 ℃. To determine the optimal annealing temperature, different measurements were performed. Based on the obtained results, the sample annealed at the lowest temperature (200 ℃) can present the highest efficiency (0.58%) by producing the highest carrier concentration and minimizing the scatter of carrier transportation in its crystalline lattice. Also, this sample shows best external quantum efficiency (EQE) about 44% and the lowest charge-transfer resistance by improving carrier collection. Finally, SCAPS simulation program was conducted evaluate the effect of the absorber's thickness and the operational temperature on the performance of the fabricated solar cells. The simulation results were further validated by conducting additional experiments. Obtained results show an increase in thickness and operational temperature resulted in a corresponding increase and decrease in the efficiency of our solar cells, respectively.