Hole-Selective Self-Assembled Monolayers Overlaid on NiOx or PEDOT:PSS for Tin-Based Perovskite Solar Cells - An Overview of Recent Characterization Methods.

Self-assembled monolayers (SAMs) with high hole-selectivity have seen growing use in the research realm of perovskite solar cells (PSCs). Even though SAMs can be used solely, their hole-selective performance is amplifiable on a p-type underlayer such as nickel oxide (NiO_x) or poly(3,4-ethylenedioxythiophene) polystyrenesulfonate (PEDOT:PSS). This is especially prominent in lead-free tin-based PSCs. Herein, we review recent relevant publications on hole-selective SAMs overlaid on NiO_x or PEDOT:PSS for tin PSCs. We first examine the characteristic features of the SAMs introduced in each publication. Since SAMs can affect the surface properties, interfacial properties, and perovskite quality, we focus on how these aspects are characterized and which methods are employed. In particular, the employed methods are various spanning computational simulations, microscopy imaging and electrochemical, spectroscopic, and crystallographic measurements. Through this review, we aim to encourage researchers to explore these aspects and methodologies in future research on hole-selective SAMs for tin PSCs.