The case of the vanishing perovskite layer

Utilizing layered perovskites (LPKs) to passivate the surface of perovskite materials is a successful strategy that currently yields state-of-the-art record-breaking devices. Nevertheless, it is not clear what happens to the LPK once other layers are processed on top. Furthermore, these LPKs can provide benefits in both p-type-intrinsic-n-type (P-I-N) and its inverted n-type-intrinsic-p-type (N-I-P) perovskite solar cell configuration, despite significant differences in their processing. In this work, we propose that this occurs due to a convergent optimization pathway, due to the thinning down and dissolution of the LPK during the deposition of subsequent layers. Here, we use X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS) to demonstrate that for most of the “processing window” employed in the literature, the LPK is severely disrupted by the deposition of charge extraction layers. Indeed, the observation of highly crystalline layers via XRD correlates with a significant reduction in short-circuit current in solar cells, counteracting any other benefits.