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%.