Oxygen Vacancy Management for High-Temperature Mesoporous SnO2 Electron Transport Layers in Printable Perovskite Solar Cells

The planar SnO2 electron transport layer (ETL) has contributed to the reported power conversion efficiency (PCE) record of perovskite solar cells (PSCs), while the high-temperature mesoporous SnO2 ETL (mp-SnO2) brings poor device performance. Herein, we report the application of mp-SnO2 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 SnO2 by reducing OVs. The introduced Mg occupies both the Sn site and interstitial site of SnO2 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-SnO2, 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 %.

Automated summary

This study demonstrates the use of magnesium (Mg) to manage oxygen vacancies (OVs) and achieve efficient printable perovskite solar cells (PSCs) with a high-temperature mesoporous SnO2 electron transport layer (ETL). The high-temperature annealing process reduces self-doping of SnO2 by reducing OVs, while the introduced Mg promotes OV formation. The synergistic effect of Mg on OVs increases carrier density and raises the Fermi level energy of the mp-SnO2 ETL, resulting in a significant improvement in device performance.