  Selecting suitable charge transport layers and suppressing non-radiative
recombination at interfaces to the absorber layer are vital to maximize the
efficiency of halide perovskite solar cells. In this work, high-quality
perovskite thin films and devices are fabricated with different fullerene-based
electron transport layers and different self-assembled monolayers as hole
transport layers. We then perform a comparative study of a significant variety
of different electrical, optical and photoemission-based characterization
techniques to quantify the properties of the solar cells, the individual layers
and importantly the interfaces between them. In addition, we highlight the
limitations and problems of the different measurements, the insights gained by
combining different methods and the different strategies to extract information
from the experimental raw data.
