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 TiO₄^4– core, functional -C-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 TiO₄^4– 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-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.