A facile solution processed ZnO@ZnS core–shell nanorods arrays for high-efficiency perovskite solar cells with boosted stability

Zinc Oxide (ZnO) has been extensively applied as electron transport material (ETM) in perovskite solar cells (PSCs) since the emergence of PSCs. However, some chemisorbed oxygen species on the surface of ZnO can cause the degradation of CH₃NH₃⁺ (MA⁺) based perovskite. To avoid the destructive effect of ZnO, a facile solution strategy was proposed to produce a ZnS shell around the ZnO nanorods arrays (ZnO-NRs), i. e. ZnO@ZnS core–shell nanorods (ZnO-NRs@ZnS). The ZnO-NRs@ZnS cascade structure can not only facilitate carrier transport, but also enhance the stability of ZnO based PSCs. A power conversion efficiency (PCE) of 20.6% was finally yielded, which is the-state-of-the-art efficiency for PSCs with one-dimensional (1D) ZnO electron transport materials (ETMs). Moreover, over 90% of the initial efficiency was retained for the unencapsulated device with ZnO-NRs@ZnS ETMs at 85 °C for 500 h, demonstrating excellent stability. This work provides a simple and efficient avenue to simultaneously enhance the photovoltaic (PV) performance and stability of 1D ZnO nanostructure-based PSCs.