LiOH Additive Triggering Beneficial Aging Effect of SnO2 Nanocrystal Colloids for Efficient Wide-Bandgap Perovskite Solar Cells

Commercial SnO2 nanocrystals used for producing electron transporting layers (ETLs) of perovskite solar cells (PSC) are prone to aggregation at room temperature and contain many structural defects. Herein, we report that the LiOH additive can simultaneously delay the aggregation and donate the beneficial aging effect to SnO2 nanocrystals. The resulting SnO2 ETLs show the desired characteristics, including a broadened absorption range, reduced defects, improved transporting properties, and decreased work function. Meanwhile, perovskite Cs0.15FA0.65MA0.20Pb(I0.80Br0.20)3 films with a wide bandgap of 1.68 eV grown on them exhibit the pure phase, higher crystallinity, fewer defects, better buried-interface contact, and more aligned energy levels with each other than the ones based on SnO2 nanocrystals without the LiOH additive and aging treatment. Hence, the average efficiencies are boosted from (18.79 ± 0.40)% to (20.16 ± 0.36)% for the resulting wide-bandgap PSCs, wherein the champion efficiency of 21.12% is achieved. In addition, the as-obtained PSCs possess good thermal and humidity stability.