(461c) Amplifying Hole Extraction Characteristics of PEDOT:PSS Via Post-Treatment with Aromatic Diammonium Acetates for Tin Perovskite Solar Cells

Tin perovskite solar cells (TPSCs) stand at the forefront as toxicity-lean technology, featuring compelling properties for example including the large light absorption coefficient, small exciton binding energy, ideal bandgap, slow hot-carrier cooling, and high charge carrier mobility. Especially, tin perovskites are adjustable to a bandgap of ~1.34 eV being optimal for single-junction solar cells according to the Shockley-Queisser limit. Beyond merely a toxicity issue, such superb properties drive TPSCs to an efficiency of power conversion (PCE) close to 15%. To close a gap with that (~26%) of lead counterparts, tailoring tin perovskites to mitigate fast crystallization and Sn(II) oxidation, and their interfaces to attain efficient and stable charge collection has proceeded. Irrespective of what types of tactics are attempted, the present-day TPSCs select poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) as hole transport layer (HTL) due to the high-performance and reproducibility in an inverted planar architecture. The PEDOT:PSS benefits from the demanding properties for TPSCs including a suitable work function (WF: ~5.0–5.2 eV), decent conductivity, and dopant-free merits. However, we should remind that the PEDOT:PSS is a commercial product and is optimized in consideration of diverse applications to leave other properties (e.g. surface properties) behind to improve to be better suited to TPSCs. We tackle this challenge via post-treatment atop the surface of PEDOT:PSS using aromatic diammonium acetate salts dissolved in a highly volatile but interactive solvent, which not only modifies PEDOT:PSS itself but also its interface with tin perovskite. The salts are embedded into PEDOT:PSS to bridge and ameliorate its interface with tin perovskite and hence to amplify its hole extraction characteristics. Consequently, we attain a high device efficiency as 12.1% and impressive stability without encapsulation for ~2800 h. The materials and methodologies of our development are extendable to other perovskites- and PEDOT:PSS-based bio, energy, and electronic applications. Moreover, they can expand on surface and interface engineering to gain broader scopes, thereby lying a critical bridging stone on paths to diverse applications.