Oxygen Vacancy Management for High-Temperature Mesoporous SnO 2 Electron Transport Layers in Printable Perovskite Solar Cells.

The planar SnO 2 electron transport layer (ETL) has contributed to the reported power conversion efficiency (PCE) record of perovskite solar cells (PSCs), while the high-temperature mesoporous SnO 2 ETL (mp-SnO 2 ) brings poor device performance. Herein, we report the application of mp-SnO 2 for efficient printable PSCs via oxygen vacancy (OV) management by introducing magnesium (Mg) into the paste. We find that high-temperature annealing suppresses self-doping of SnO 2 by reducing OVs. The introduced Mg occupies both the Sn site and interstitial site of SnO 2 and promotes the formation of OVs. Lattice Mg tends to induce neutral OVs and interstitial Mg could promote the ionization of neutral OVs for self-doping. The synergy effect on OVs increases the carrier density and upshifts the Fermi level energy of mp-SnO 2 , ensuring its capability as the well-performed ETL with trap-less charge transport and suppressed surface recombination for dramatic improved device PCE from 6.62 % to 17.25 %.