Prospect of SnO 2 Electron Transport Layer Deposited by Ultrasonic Spraying

The SnO 2 electron transport layer (ETL) has been characterized as being excellent in optical and electrical properties, ensuring its indispensable role in perovskite solar cells (PSCs). In this work, SnO 2 films were prepared using two approaches, namely, the ultrasonic spraying method and the traditional spin-coating, where the different properties in optical and electrical performance of SnO 2 films from two methods were analyzed by UV–Vis, XRD, AFM, and XPS. Results indicate that the optical band gaps of the sprayed and the spin-coated film are 3.83 eV and 3.77 eV, respectively. The sprayed SnO 2 film has relatively low surface roughness according to the AFM. XPS spectra show that the sprayed SnO 2 film has a higher proportion of Sn 2+ and thus corresponds to higher carrier concentration than spin-coated one. Hall effect measurement demonstrates that the carrier concentration of the sprayed film is 1.0 × 10 14 cm −3 , which is slightly higher than that of the spin-coated film. In addition, the best PCSs efficiencies prepared by sprayed and spin-coated SnO 2 films are 18.3% and 17.5%, respectively. This work suggests that the ultrasonic spraying method has greater development potential in the field of flexible perovskite cells due to its feasibility of large-area deposition.