Highly efficient inverted planar perovskite solar cells from TiO₂ nanoparticles modified interfaces between NiO hole transport layers and conductive glasses

It has been demonstrated that the interfaces in perovskite solar cells (PSCs) have significant influence on photovoltaic performance of PSCs. So interface engineering is very important for achieving high power conversion efficiency (PCE). However, an important interface of fluorine-doped tin oxide conductive glass (FTO)/hole transport layer (HTL) in the inverted planar PSCs is customarily missed. Here, we verify that through modification of the interface between FTO and NiO HTL with ultra-small TiO₂ nanocrystals (NCs), the PCE of inverted planar PSCs can be obviously enhanced from the original 15.23% to the highest value of 16.21%. The optical transmittance spectra show that the TiO₂ NCs modification has little influence on the transparency of the substrates. The PL and TRPL data reveal clearly enhanced hole-extracting speed owing to the improve coverage and quality of the NiO HTLs on TiO₂ NCs-modified FTOs. These features are important reasons for the improved photovoltaic performance of the corresponding devices. This work highlights an effective way for enhancing photovoltaic performance of the inverted planar PSCs through modifying the interfaces between the transparent conductive substrates and the HTLs.