Manipulating SnO2 Growth for Efficient Electron Transport in Perovskite Solar Cells

Solution-processed tin oxide (SnO2) is ubiquitously used as the electron transport layer (ETL) in perovskite solar cells, while the main concerns related to the application of SnO2 nanoparticles are the self-aggregation potential and infeasible energy level adjustment, leading to inhomogeneous thin films and mismatched energy alignment with perovskite. Herein, a novel route is developed by adding a functional titanium diisopropoxide bis(acetylacetonate) (TiAcAc) molecule, comprising TiO44- core, functional -C(sic)O, and long alkene groups, into the SnO2 nanoparticle solution, to optimize the electronic transfer property of SnO2 for efficient perovskite solar cells. It is found that the TiO44- can be used to tune the electronic property of the SnO2 layer, and the long alkenes can act as a stabilizer to avoid the nanoparticle aggregation and electronic glue among the SnO2 nanoparticles in the eventual nanoparticulate thin film, enhancing its homogeneity and conductivity. Furthermore, the residual -C(sic)O groups on the ETL surface can strongly associate with the Pb2+ and improve the interface intimacy between the ETL and perovskite. As a result, the efficiency of perovskite solar cells can be boosted from 18% to above 20% with significantly reduced hysteresis by employing SnO2-TiAcAc as electron transport layer, indicating a great potential for efficient perovskite solar cells.