Roll-to-roll slot-die coating of PTAA with PEDOT:PSS buffer layer for perovskite solar cells: coating analysis by XPS mapping

Abstract

Roll-to-Roll (R2R) deposition offers a promising route for scaling up the production of perovskite solar cells (PSCs); however, the performance of R2R-fabricated devices still lags behind those produced through laboratory-scale methods. One significant factor contributing to this performance gap, particularly in P–I–N structured devices, is the use of suboptimal hole transport layers (HTLs), such as poly(3,4-ethylenedioxythiophene)–polystyrenesulfonate (PEDOT:PSS). In this study, we explore the potential of replacing PEDOT:PSS with poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA), a more efficient and stable HTL. While undoped PTAA alone shows promise, its application on the rough surface of PET-ITO substrates is insufficient to fully replace PEDOT:PSS, leading to reduced device performance. However, when combined with a PEDOT:PSS buffer layer, PTAA demonstrated significant improvements, achieving a power conversion efficiency (PCE) of 15.2% compared to 12.6% with PTAA alone using R2R deposition. To better understand the coating characteristics and interactions of these materials, we conducted a detailed analysis of the surface topography of PET-ITO and the HTL layer using X-ray photoelectron spectroscopy (XPS) mapping. This study provides critical insights into the synergistic effects of PEDOT:PSS and PTAA, highlighting their combined potential for enhancing the efficiency of R2R-fabricated PSCs.