Hole transport layer NiOx-based inverted perovskite solar cells (PSCs) have advantages of simple fabrication, low temperature, and low cost. Furthermore, the p-type NiOx material compared to that of typical n-type SnOx for PSCs has better photostability potential due to its lower photocatalytic ability. However, the NiOx layer modified by some typical materials show relatively simple functions, which limit the synthesized performance of NiOx-based inverted PSCs. Phenethyl ammonium iodide (PEAI) was introduced to modify the NiOx/perovskite interface, which can synchronously contribute to better crystallinity and stability of the perovskite layer, passivating interface defects, formed quasi-two-dimensional PEA2PbI4 perovskite layers, and superior interface contact properties. The PCEs of PSCs with the PEAI-modified NiOx/perovskite interface was obviously increased from 20.31 from 16.54% compared to that of the reference PSCs. The PSCs with PEAI modification remained 75 and 72% of the original PCE values aging for 10 h at 85 °C and 65 days in a relative humidity of 15%, which are superior to the original PCE values (47 and 51%, respectively) for the reference PSCs. Therefore, PSCs with the PEAI-modified NiOx/perovskite interface show higher PCEs and better thermal stability and moisture resistance.

Surface modification engineering is an effective method to improve the crystallinity and passivate the perovskite interface and grain boundary, which can improve the power conversion efficiency (PCE) and stability of perovskite solar cells (PSCs). The typical interface modification method is usually introduced at the interface of the perovskite/hole transport layer (HTL) or perovskite/electron transport layer (ETL) through coordination of the groups in the material with the perovskite. In this work, the n-type semiconductor bathocuproine (BCP) including the pyridine nitrogen bond was modified at the interfaces of perovskite/HTL or perovskite/ETL to improve perovskite crystallinity and interface contact properties. The better crystallinity and superior interface contact properties are obtained using BCP unilateral modification, which obviously increases the PCEs of PSCs. The BCP bilateral modification at both perovskite/ETL and perovskite/HTL interfaces can further improve the crystallinity with fewer defects and superior contact properties, which show the largest V oc (1.14 V) and fill factors (FF 77.1%) compared to PSCs with BCP unilateral modification. PSCs with BCP bilateral modification obtained 20.6% PCEs, which is greatly higher than that (17.5%) of the original PSCs. The stability of PSCs with BCP bilateral modification can be greatly improved due to the better crystal quality and hydrophobic property of the interfaces. The results demonstrated that the n-type BCP material can efficiently modify both perovskite/HTL and perovskite/ETL interfaces beyond its semiconductor type, which can greatly improve the PCEs and stability of PSCs because BCP modification can passivate interfaces, improve interface contact and hydrophobic properties, promote crystallinity of the perovskite layer with fewer defects, and block carrier recombination at both interfaces.

In recent years, the power conversion efficiency (PCE) of NiOx-based perovskite solar cells (PSCs) has increased by leaps and bounds, reaching more than 20%. However, the structure of PSCs is unstable under high humidity, high temperature, and UV irradiation environment, which is easily decomposed. To improve the limitations of the typical structure of the perovskite layer, the strategy of p-type poly­(9-vinylcarbazole) (PVK) doped with a small amount of [6,6]-phenyl-C61-butyric acid methyl (PCBM) has been developed to modify the interface between the perovskite layer and the electron transport layer (ETL). A dense quasi-two-dimensional structure layer is formed onto the three-dimensional perovskite layer, and better crystallinity of perovskite with less defects and superior contact properties at the perovskite/PCBM interface can be obtained under PCBM-doped PVK modification, which improve perovskite stability, boost carrier transport and extraction, and reduce carrier recombination. Furthermore, the PCBM-doped PVK-modified layer further boosts electron tunneling from the perovskite layer to PCBM ETL assisted with PCBM dopants. Therefore, PCEs of Sr@NiOx-based PSCs with PCBM-doped PVK modification were increased to 20.91 from 16.54% of the reference PSCs. Furthermore, PSCs with PCBM-doped PVK modification show better anti-UV, moisture, and thermal resistance.