Band Engineering via Sn‐doping of Zinc Oxide Electron Transport Materials for Perovskite Solar Cells

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The performance of planar perovskite solar cells (PSCs) is quite dependent on the interfacial conditions and then the interfacial band engineering is very important not only for the effective improvement of power conversion efficiency (PCE) but also for the better understanding of the charge transfer in the cells. In this report, the band engineering of the ZnO based electron transport layer (ETL) in PSCs was studied by modulating Sn‐doping level (0 ≤ x ≤ 0.2). A V ‐like variation of work function ( W f ) as function of Sn‐doping level in Zn 1‐ x Sn x O 1+ x films was realized from 4.23 to 4.39 eV. As a result, the photovoltaic performance of PSCs with the Zn 1‐ x Sn x O 1+ x ETLs was adjusted and the V ‐like tendencies of photovoltaic parameters of devices, such as open‐circuit voltage ( V OC ) and the short‐circuit current ( J SC ), were found. The maximum values of V OC and J SC were achieved as 1.04 V and 20.68 mA cm −2 with an ETL of Zn 1‐ x Sn x O 1+ x , respectively, which corresponds to a highest PCE of 14.12% for ZnO‐based pervoskite solar cells with a large fill factor of 65.62.