Amplifying Hole Extraction Characteristics of PEDOT:PSS via Post-treatment with Aromatic Diammonium Acetates for Tin Perovskite Solar Cells

We modify the PEDOT:PSS hole transport layer (HTL), commonly adopted for high-performance tin perovskite solar cells (TPSCs), via post-treatment of its surface using aromatic diammonium acetate salts dissolved in a highly volatile but interactive solvent. The solvent partly etches excessive insulating PSS while enabling tight anchoring of the salts to the PEDOT:PSS HTL. The salts improve not only the PEDOT:PSS/perovskite interface but also the top surface of tin perovskite thin films, leading to reduced interface defects, larger built-in potentials, and suppressed perovskite pinhole defects. In addition, the salts transform the PEDOT structure from benzoid to quinoid and depopulate excessive hole charge carriers to promote hole extraction. Consequently, TPSCs attain a high efficiency of 12.1% under standard 1 sun light illumination and impressive stability without encapsulation for ∼2800 h under an N2 atmosphere. We developed a straightforward but impactful method to modify PEDOT:PSS for broader applications.