High performance planar perovskite solar cells by ZnO electron transport layer engineering

• Published in: Nano energy 2017-09, Vol.39, p.400-408
• Main Authors: An, Qingzhi, Fassl, Paul, Hofstetter, Yvonne J., Becker-Koch, David, Bausch, Alexandra, Hopkinson, Paul E., Vaynzof, Yana
• Format: Article
• Language: English
• Subjects: Extraction layer engineering; Perovskite solar cells; ZnO
• ISSN: 2211-2855
• DOI: 10.1016/j.nanoen.2017.07.013

ZnO as electron extraction layer in photovoltaic devices has many advantages, including high mobility and low processing temperature. However, it has been underutilized in perovskite solar cells due to the reported instabilities of perovskite layers deposited on ZnO resulting in poor device performance. Herein, we modify the ZnO layer by incorporating Cs or Li dopants in its bulk and depositing a self-assembled monolayer on its surface. This combined approach of engineering both the bulk and surface properties of ZnO results in significant improvements in the performance of planar MAPbI3 perovskite solar cells with a maximum power conversion efficiency of 18%, accompanied by a reduction in hysteresis and a significant enhancement of the device stability. Our work makes engineered solution-processed ZnO layers a practical alternative to TiO2 as electron extraction layers in perovskite solar cells, while also eliminating the need for high temperature sintering steps from the device fabrication. [Display omitted] •ZnO extraction layers are engineered using doping and a modification with a self-assembled monolayer (SAM).•This results in PCEs up to 18%, accompanied by reduced hysteresis and improved stability.•Modification with a SAM improves the perovskite film formation, while doping reduces the density of traps in the ZnO bulk.•All modifications are performed in solution at low temperature and are applicable to printed and flexible perovskite solar cells.