Bilayer SnO2 as Electron Transport Layer for Highly Efficient Perovskite Solar Cells

Tin oxide (SnO2) has been reported as a promising electron transport layer (ETL) for planar heterojunction perovskite solar cells (PSCs). This work reports a low temperature solution-processed bilayer SnO2 as an efficient ETL in gas-quenched planar-heterojunction methylammonium lead iodide (MAPbI(3)) perovskite solar cells. SnO2 nanoparticles were employed to fill the pin-holes of sol-gel SnO2 layer and form a smooth and compact bilayer structure. The PCE of bilayer devices has increased by 30% compared with sol-gel reference device and the J(sc), V-oc, and FF has been improved simultaneously. The superior performance of bilayer SnO2 is attributed to the reduced current leakage, enhanced electron extraction characteristics, and mitigated the trap-assisted interfacial recombination via X-ray photoelectron spectroscopy (XPS), electrochemical impedance spectroscopy (EIS), and space-charge limited current-voltage (SCLC) analysis.