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 (MAPbI3) 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 Jsc, Voc, 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.