Interfacing green synthesized flake like-ZnO onto TiO <sub/>2</sub> as a bilayer electron extraction for efficient perovskite solar cells

摘要： To improve the performance of the PSCs, it is essential to prevent the carrier recombination losses at the interfaces of the transparent metal oxide electrode/electron transport layer (ETL) / active absorber perovskite layer. This present work reports about the green synthesis approach used for the preparation of flake like-ZnO nanostructure (GF-ZnO NSs), naturally extracted from the leaf of Albizia Amara - as a reducing cum capping agent. Herein, we have introduced the above prepared an n-type GF-ZnO NSs material as efficient electron transport interfacial layer (bi-ETL) at the ETL/perovskite junction in the fabricated perovskite solar cells (PSCs). The structure of the fabricated PSC device as follow: Glass/ITO/bi-ETL (c-TiO2/GF-ZnO NSs)/CH3NH3PbI3-xClx/Spiro-MeOTAD/Au. A comparative study has also been made by deploying electron transport materials such as c-TiO2 and GF-ZnO NSs separately. From this, it has been found that the bi-ETL perovskite solar cell devices achieved a maximum power conversion efficiency (PCE) of 7.83% with open-circuit voltage (VOC) of 0.728 V, short circuit current density (JSC) of 20.46 mA/cm2 and a fill factor (FF) of 52.61% compared to that of the chemically reduced ZnO based devices. Whereas, the c-TiO2, GF-ZnO NSs and the chemically reduced CR-ZnO based ETL based devices achieved a PCE of 4.84%, 5.82% and 6.81% respectively. The obtained better performance of the bi-ETL based devices is ascribed to the enhanced carrier extraction and the reduced recombination losses at the interface between the ETL and the active perovskite layer.