Unraveling the morphological and energetic properties of 2PACz self-assembled monolayers fabricated with upscaling deposition methods

Abstract

Self-assembled monolayers (SAMs) are widely used as hole transport materials in inverted perovskite solar cells, offering low parasitic absorption and suitability for semitransparent and tandem solar cells. While SAMs have shown to be promising in small-area devices (≤1 cm2), their application in larger areas has been limited by a lack of knowledge regarding alternative deposition methods beyond the common spin-coating approach. Here, we compare spin-coating and upscalable methods such as thermal evaporation and spray-coating for [2-(9H-carbazol-9-yl)ethyl]phosphonic acid (2PACz), one of the most common carbazole-based SAMs. The impact of these deposition methods on the device performance is investigated, revealing that the spray-coating technique yields higher device performance. Furthermore, our work provides guidelines for the deposition of SAM materials for the fabrication of perovskite solar modules. In addition, we provide an extensive characterization of 2PACz films focusing on thermal evaporation and spray-coating methods, which allow for thicker 2PACz deposition. It is found that the optimal 2PACz deposition conditions corresponding to the highest device performances do not always correlate with the monolayer characteristics.