Control of Surface Defects in ZnO Nanorod Arrays with Thermally Deposited Au Nanoparticles for Perovskite Photovoltaics

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DOI http://dx.doi.org/10.1021/acsaem.9b00452
Reference Tulus, S. Olthof, M. Marszalek, A. Peukert, L.A. Muscarella, B. Ehrler, O. Vukovic, Y. Galagan, S.C. Boehme and E. von Hauff, Control of Surface Defects in ZnO Nanorod Arrays with Thermally Deposited Au Nanoparticles for Perovskite Photovoltaics, ACS Appl.Energy Mater. 2, 5: 3736-3748 (2019)
Group Hybrid Solar Cells

In this work, we employ vacuum deposited Au nanoparticles (∼4 nm) to control the defect density on the surface of hydrothermally synthesized ZnO nanorod arrays (ZnO-NR), which are of interest for electron-transport layers in perovskite solar cells. Using a combination of photoluminescence spectroscopy, X-ray photoelectron spectroscopy, and ultraviolet photoelectron spectroscopy, we show that the Au particles reduce the presence of defects in the ZnO-NR. We discuss this in terms of trap filling due to band bending at the ZnO-NR surface. As a proof-of-concept, we apply the Au-decorated ZnO-NR as electron-transport layers in mixed-cation and mixed-halide lead perovskite solar cells (Cs0.15FA0.85PbI2.75Br0.25). Devices prepared with the Au-decorated ZnO-NR electron-transport layers demonstrate higher open-circuit voltages and fill factors compared to solar cells prepared with pristine ZnO-NR, resulting in an increase in the power-conversion efficiency from 11.7 to 13.7%. However, the operational stability of the solar cells is not improved by the Au nanoparticles, indicating that bulk properties of the perovskite may limit device lifetime.