Nickel oxide (NiO) materials with excellent stability and favorable energy bands are desirable candidates for hole‐selective contact (HSC) of inverted perovskite solar cell (PSC). However, studies that focus on addressing interfacial issues, which are induced by the poor NiO/perovskite contact or other defects, are scarce. In this study, a facile one‐step hydrothermal strategy is demonstrated for the development of a 3 D NiO nanowall (NW) film as a promising HSC. The new NiO NWs HSC exhibits a robust and homogenous mesoporous network structure, which improved the NiO/perovskite interface contact, passivated the interfacial defect and improved the quality of the perovskite film. The optimized interface features enabled a power conversion efficiency (PCE) approaching 18 %. A diethanolamine (DEA) interlayer was introduced to further passivate the intrinsic defect of the NiO surface, resulting in better charge transfer with suppressed recombination loss. As a result, the champion PCE of the NiO NWs/DEA‐based device was increased to 19.16 % with a high open‐circuit voltage (≈1.11 V) and fill factor (>80 %), which is prominent in methylammonium lead iodide‐based inverted PSCs. Furthermore, the device exhibited better stability and lower hysteresis behavior than a conventional solution‐based NiO nanocrystal device.

Essentially, detrimental defects distributed at perovskite surface and grain boundaries (GBs) directly impede the further enhancement of both the photovoltaic performance and long-term stability of perovskite solar cells (PSCs). Herein,...

Inverted perovskite solar cells (PSCs) demonstrate attractive features in developing an air-stable photovoltaic device, by employing inorganic hole transport layers (HTLs). However, their power conversion efficiencies are still inferior to that of mesoporous n-i-p devices, mainly attributed to the undesirable hole extraction and interfacial recombination loss. Here, we design a novel one-dimensional NiO nanotube (NT) nanoforest as efficient mesoporous HTLs. Such a NiO NT mesoporous structure provides a highly conductive pathway for rapid hole extraction and depresses interfacial recombination loss. Furthermore, excellent light capturing could be achieved by optimizing the length and branch growth of the NiO NT nanoforest, which mimics the evolution of the natural forest. Therefore, this inverted mesoporous PSCs yield an optimal efficiency of 18.77%, which is still prominent in state-of-the-art NiO-based devices. Alternatively, the mesoporous device exhibits greatly improved long-term stability. This work provides a new design perspective for developing high-performance inverted PSCs.

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