Interface engineering with NiO nanocrystals for highly efficient and stable planar perovskite solar cells

It is verified that the interface engineering is an effective way to achieve highly efficient and stable perovskite solar cells. However, the typical interface engineering of using insulating polymer or metal oxide to fabricate tunneling layers has an obvious drawback that is their thickness must be exactly controlled (usually <2 nm), thinner or thicker film will not bring positive effects on the photovoltaic performance of the device. Here we report the fabrication of efficient and stable planar perovskite solar cells by interface engineering with p-type NiO nanocrystals. It is found that the photovoltaic performance of the devices is not so sensitive to the thickness of NiO thin films. The champion planar perovskite solar cell with a NiO thin film in the interface of perovskite/spiro-OMeTAD can achieve a high efficiency of 19.89% and a high steady-state power output of 19.37 mW cm−2, being attributed to the significantly suppressed radiative recombination and eliminated charge accumulation. Moreover, the device shows excellent stability because its efficiency can retain 94.40% of the initial value after 400 h measurement in an air environment with 50 ± 5% relative humidity. Therefore, this work supplies an easy way to implement interface engineering for boosting both efficiency and stability of perovskite solar cells.