Forming a composite electron blocking layer to enhance the performance of carbon-based CsPbI₃ perovskite solar cells

Carbon-based CsPbI₃ perovskite solar cells (C-PSCs) have attracted much interest due to their high chemical stability. However, their efficiency still largely lags behind those achieved by conventional CsPbI₃ PSCs because of the electron back transfer from the perovskite to the carbon electrode. Herein, we address the above issue by forming a composite electron blocking layer at the CsPbI₃/carbon interface. The CsPbCl₃ quantum dots (QDs) layer is first deposited on the CsPbI₃ film by spin coating a QDs solution, while the Cs₂PbI₂Cl₂ nanosheets are then generated on the surface by the post treatment of a CsCl solution. The composite blocking layer not only well suppresses electron back transfer but also passivates crystal defects. As a result, the efficiency of CsPbI₃ C-PSCs is boosted from 12.51% to 16.10%.