Ozone-Treated Aluminum Doped Zinc Oxide for ETL-Free Stable Perovskite Solar Cells

Aluminum doped zinc oxide (AZO) can function as effective electronic transport layer (ETL) cum transparent electrode for perovskite solar cells. Measured electronic band diagram shows that AZO/perovskite is a carrier-selective interface that blocks holes but allows transport of electrons. The performance of AZO/perovskite interface is significantly improved by exposing AZO surface to ozone. Ozone depletes carriers from top few nanometers of AZO, forming AZO/un-doped-AZO/perovskite interface with lower recombination losses, resulting in champion cell efficiency of 10.5% and open circuit voltage (Voc) up to 1.05V. AZO interface is also stable. Devices retained 90% of initial Voc even after 60 days of ambient storage.