Perovskite solar cells (PSCs) are not all about perovskites, according to Sofia Apergi, who started less than a year ago to work on another important part of the PSCs, the charge transport layer, NiO in this case. The manuscript is recently accepted for publication by Physical Review Materials and available at arXiv. This is our first publication on line of interface of perovskites/transport materials achieved within less than a year. Congratulations, Sofia!

Abstract: The performance of a PSC depends on the combination and alignment of all its comprising layers, such as electrodes and charge transport layers. NiO is a very promising hole transport layer and its electronic levels need to be optimally aligned with a given perovskite for maximum PSC efficiency. Applying surface modifiers is one of the most widespread strategies to tune its energy levels.  In this work, we investigated the effect of single layer adsorption of twenty different alkali halides on the electronic levels of NiO, using Density Functional Theory (DFT). Our results show that alkali halides can shift the position of the valence band maximum (VBM) of NiO to a surprisingly large extend in both directions, from -3.10 eV to +1.59 eV. Our results indicate that with alkali halide surface modifiers, the electronic levels of NiO can be tuned robustly and potentially match those of many perovskite compositions in perovskite solar cells.