Perovskite is a promising photovoltaic material in the sustainable energy field. In inverted perovskite solar cells (PSCs), the bottom p-type hole transport materials play a crucial role in the device power conversion efficiency (PCE) and ambient stability. Nickel oxide (NiO X ) is the most promising inorganic hole transport material for inverted PSCs. However, the inferior interfacial contact of NiO X /perovskite has limited the improvement of inverted PSC performance. Strategies for handling this interfacial contact issue are scarce, and most of them require expensive equipment and complex preparation procedures. Herein, a new facial route was introduced to enhance the NiO X /perovskite interfacial contact using a porous morphology produced with a polyvinyl butyral (PVB) additive. Moreover, a bilayer-NiO X hole transport layer structure was successfully designed and used for fabricating a high-performance inverted PSC. The device exhibited a PCE of 17.57% and sufficient stability in ambient air. Various characterizations were performed to investigate the effect of the bilayer-NiO X film on device performance. The PSC exhibited superior performance, which was because of the enhanced perovskite film quality and the excellent bilayer-NiO X charge transfer ability and trap density reduction.

The photovoltaic property of perovskite solar cells (PSCs) is affected by detrimental defects located at the bulk and surface of perovskite films. Furthermore, defect passivation of the perovskite films is challenging. Herein, we add solid CsCl to PbI 2 precursor solutions to adjust the properties of PbI 2 membranes and obtain perovskite layers with a micrometer-sized grain by reducing grain boundary defects. Bulk defects are reduced by the increase in grain size and decrease in grain boundaries. Fewer bulk defects and the incorporation of Cs increase the device performance, improving the power conversion efficiency (PCE) from 19.72% to 22.24% and suppressing hysteresis. The passivation of surface defects further increases the PCEs and open-circuit voltages (V OC ) of PSCs. Therefore, we use 4-methoxyphenethylamine (CH 3 O−PEAI) to modify the CsCl perovskite films to eliminate the surface defects and suppress nonradiative charge recombination. The surface defect passivation using CH 3 O−PEAI further improves the PCE of the PSCs to 23.25% with a V OC of 1.186 V, resulting in more efficient and stable PSCs.

Organic spacers play a crucial role in two-/three-dimensional (2D/3D) hybrid perovskite-based solar cells that integrate the advantages of the stability of 2D perovskites and the high efficiency of 3D perovskites. However, improving the stability of the device without compromising the high photovoltaic efficiency in 2D/3D perovskite solar cells using large organic cations in 2D perovskite is a challenge. Herein, we synthesized 2-thiopheneethylammonium iodide (TEAI) and found that TEAI can perform as a spacer for 2D/3D hybrid perovskites. TEAI with a bulky aromatic spacer in 2D/3D hybrid perovskites can effectively induce crystalline growth and orientation, leading to a longer carrier lifetime, higher carrier mobility, fewer surface, and grain boundary defects. The inclusion of TEAI also improves surface hydrophobicity. The 2D/3D hybrid perovskite device based on TEAI achieved the highest efficiency of 18.75% compared with the 16.83% efficiency of the 3D perovskite device. After aging for 1000 h in an ambient atmosphere, the unpackaged 2D/3D hybrid perovskite solar cells maintained approximately 82% of their initial efficiency, whereas that of the controlled devices decreased to approximately 47% of their original performance. These results suggest that TEAI can be used as an organic spacer for the preparation of high-efficiency and high-stability 2D/3D perovskite solar cells.

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