Toward high-efficiency perovskite solar cells with one-dimensional oriented nanostructured electron transport materials

The unique advantages of one-dimensional (1D) oriented nanostructures in light-trapping and charge-transport make them competitive candidates in photovoltaic (PV) devices. Since the emergence of perovskite solar cells (PSCs), 1D nanostructured electron transport materials (ETMs) have drawn tremendous interest. However, the power conversion efficiencies (PCEs) of these devices have always significantly lagged behind their mesoscopic and planar counterparts. High-efficiency PSCs with 1D ETMs showing efficiency over 22% were just realized in the most recent studies. It yet lacks a comprehensive review covering the development of 1D ETMs and their application in PSCs. We hence timely summarize the advances in 1D ETMs-based solar cells, emphasizing on the fundamental and optimization issues of charge separation and collection ability, and their influence on PV performance. After sketching the classification and requirements for high-efficiency 1D nanostructured solar cells, we highlight the applicability of 1D TiO₂ nanostructures in PSCs, including nanotubes, nanorods, nanocones, and nanopyramids, and carefully analyze how the electrostatic field affects cell performance. Other kinds of oriented nanostructures, e.g., ZnO and SnO₂ ETMs, are also described. Finally, we discuss the challenges and propose some potential strategies to further boost device performance. This review provides a broad range of valuable work in this fast-developing field, which we hope will stimulate research enthusiasm to push PSCs to an unprecedented level.