Optical, structural, morphological and electrical characterization of ZnO:S electron transport layer for enhanced-efficiency perovskite solar cell

Perovskite solar cells (PSCs) have become popular for research due to their advanced optical properties and ease of preparation. They have shown high power conversion efficiencies, broad photo-absorption wavelengths and good charge carrier mobilities. However, they still face chemical and thermal instabilities that generate insufficiently controlled interfaces between the perovskite, transport layer and contacts. In this work zinc oxide (ZnO) was used as electron transport material (ETM), which has shown high performance in different semiconductor materials. The stability of the fabricated perovskite-based solar cell was enhanced by incorporating sulphur in ZnO (ZnO:S). The dopant was varied from 0.02 M (4% sulphur doping) to 0.08 M (16% sulphur doping) concentration. The synthesized material was characterized to determine their structural, optical and morphological properties using X-ray diffraction (XRD), ultraviolet-visible spectroscopy (UV-Vis) and scanning electron microscopy (SEM), respectively. The boxplot analysis of results was conducted showing that ZnO:4%S performed best. Ageing test shown an initial good performance for ZnO:4%S. However, on close observation near 500 h time, it had decayed a little bit faster than the device fabricated with ZnO:8%S electron transport layer (ETL). Therefore, it can be concluded that lower sulphur doping concentration leads to better performance. However, more doping concentrations increases stability and therefore balancing performance and doping maybe required. A power conversion efficiency (PCE) of 16.5%, short-circuit current density (Jsc) of 21.3 mAcm −2 and open circuit voltage (Voc) of 1.15 V were obtained.