Interfacial Modification of Sol-Gel ZnO/AZO Bilayer as Highly Efficient Electron Transport Layer for Perovskite Solar Cells

We report an interfacial modification of sol-gel ZnO/Al-doped ZnO (AZO) bilayer thin film as the electron transport layer (ETL) in the perovskite solar cells. We found that the power conversion efficiency (PCE) of perovskite solar cells was significantly increased from 11.28% to 14.24% with short-circuit current density (J
_sc
) of 19.53 mA cm
^-2
, open-circuit voltage (V
_oc
) of 1.12 V, and fill factor (FF) of 65.1% by employing the AZO thin film as the buffer layer. Moreover, the enhancement in performance was obtained through energy-level offset adjustment of AZO thin film, which allows the better charge separation of perovskite solar cells.