Self‐Assembled Monolayers for Highly Efficient All‐Polymer Solar Cells Sequentially Processed from Hydrocarbon Solvent

Abstract All‐polymer solar cells (all‐PSCs), comprising polymer donors and polymerized small‐molecule acceptors (PSMAs), hold significant promise for industrial production owing to their superior device efficiencies and stability. However, the lower molecular weights and weaker crystallinity of PSMAs lead to low electron mobility, while achieving high efficiencies in all‐PSCs typically rely on the use of the highly volatile chloroform. These challenges have been addressed through the development of self‐assembled monolayers (SAMs) as a novel interfacial layer, offering improved transparency, stability, sensitivity and surface passivation. This research investigates SAMs, specifically 2PACz, as a hole transporting layer (HTL) in all‐PSCs, employing a sequential processing strategy with toluene solvent to mitigate the aforementioned challenges. This study achieves highly efficient 2PACz‐based all‐PSC cells at 19.19% (certificated at 18.51%), which is a new record for all‐PSCs by non‐halogen solvents. Compared to PEDOT:PSS‐based solar cells, the improved performance of 2PACz‐based devices can be attributed to enlarged charge carrier mobility, prolonged carrier lifetime, and constrained recombination traps. Good generality of 2PACz as HTL is observed for PM6:PYF‐T‐ o and PM6:PJ1‐γ systems as 2PACz‐based devices outperform PEDOT:PSS counterparts. These results demonstrate that SAMs are a promising candidate for hole transport engineering in high‐performance all‐PSCs.