Silicon/nickel oxide core/shell nanospheres as a hole transport layer for high efficiency and light-stable perovskite solar cells.

Metal halide perovskite solar cells (PSCs) possess huge potential due to their high power conversion efficiency. However, instability is still a key factor limiting their applications. Therefore, we have found a feasible strategy to improve the light stability of PSCs. Specifically, a core-shell material with a silicon nanosphere core and a nickel oxide nanosheet shell serves as the hole transport layer in our PSCs. Due to the selective absorption of ultraviolet light by the silicon nanoparticles, the ultraviolet light content of the natural light that reaches the perovskite layer is reduced. Compared with a control device (without Si), the PSCs with the silicon/nickel oxide hole transport layer possessed a higher current density of 22.09 mA cm-2 and a higher power conversion efficiency of 18.54%, with both values increased by 2.7% and 6.1%, respectively. More importantly, the PSCs based on a silicon/nickel oxide hole transport layer maintains 85% of its initial power conversion efficiency value after 700 hours of natural light exposure. These results indicate that the silicon/nickel oxide hole transport layer is an important functional component of the PSCs, which improves the photovoltaic performance and reduces ultraviolet light-induced photodegradation, thereby improving the device stability.

3 D NiO Nanowall Hole-Transporting Layer for the Passivation of Interfacial Contact in Inverted Perovskite Solar Cells.

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.

Minimalist Design of Efficient, Stable Perovskite Solar Cells.

Feasible production process and excellent device stability are significant prerequisites for the practical application of perovskite solar cells (PSCs). Herein, a systemic strategy is developed to fabricate stable, minimalist PSCs without a conventional electron/hole transport layer. The engineering is carried out by surface modification of the fluorine-doped tin oxide (FTO) substrate and incorporation of perovskite film with NiO nanoparticles (NPs). Notably, the surface modification can impart an unexpected porous structure to the FTO substrate, thereby facilitating efficient diffusion and deposition of perovskite. Besides, the incorporated NiO NPs passivate the defects of perovskite film, resulting in the increase of perovskite grain size, decrease of grain boundary density, and increase of film thickness. Synergistic improvements in film quality and interfacial contact enhance charge transport/extraction capacity and suppress electron/hole recombination. Consequently, the stabilized efficiency of 14.65% is realized for this modified FTO/MAPbI3-NiO/Ag device, with excellent moisture and thermal stability. Overall, this work provides a viable strategy for accelerating the commercialization of PSCs due to the significant process simplification and cost reduction.

Novel NiO Nanoforest Architecture for Efficient Inverted Mesoporous Perovskite Solar Cells.

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.