Enhancing Efficiency and Durability of Inverted Perovskite Solar Cells with Phenol/Unsaturated Carbon-Carbon Double Bond Dual-Functionalized Poly(3,4-ethylenedioxythiophene) Hole Extraction Layer

Lignosulfonate (LS) with lots of active phenol and unsaturated carbon-carbon double bond groups is applied as template and dispersant to prepare a PEDOT:LS complex which possesses some superior properties including high work function (WF), superior homogeneity, and excellent waterproofness compared to the popular conducting polymer, poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS). The reactivity of phenol and unsaturated carbon-carbon double bond groups can result in a covalent bonding between LS and PEDOT, improving the homogeneity of PEDOT:LS. The thermal cross-linking activity of phenol and unsaturated carbon-carbon double bond groups can result in a dense PEDOT:LS film with excellent waterproofness. Inspired by the aforementioned merits, PEDOT:LS is applied as hole extraction layer (HEL) in an inverted methylammonium-lead iodide perovskite solar cell (PSC). The PEDOT:LS-based PSC shows an enhanced power conversion efficiency (PCE) of 12.85%, outperforming the PEDOT:PSS reference device exhibiting a PCE of 12.10% owing to the enhanced WF and homogeneity of HEL. More importantly, the PEDOT:LS-based PSC shows a higher long-term stability compared with the PEDOT:PSS reference device due to the excellent waterproofness of HEL. Our research provides a strategy for developing a new template for a conducting polymer based on lignin, a rich renewable biomass containing lots of active phenol and unsaturated carbon-carbon double bond groups.