Stabilizing Solution-Substrate Interaction of Perovskite Ink on PEDOT:PSS for Scalable Blade Coated Narrow Bandgap Perovskite Solar Modules by Gas Quenching
Abstract
The development of scalable 1.25 eV mixed Pb-Sn perovskite solar modules by blade coating lags behind Pb-based perovskites due to limited understanding of solution-substrate interaction of the perovskite ink on PEDOT:PSS and subsequent gas quenching. To address this challenge, we systematically studied the wet film deposition and quenching process to better understand narrow bandgap perovskite film formation on PEDOT:PSS. We found, the wetting of Pb-Sn perovskite ink on PEDOT:PSS is highly unstable over relevant coating time scales, causing the contact angles to decrease rapidly from 42 to 16 within seconds. This instability leads to localized irregularities in the wet film, resulting in uneven solvent extraction and inhomogeneous nuclei density. As a result, rough perovskite films with voids at the buried interface are obtained. To overcome this problem, we developed a quasi-static wetting process by reducing the blade coating speed, thereby stabilizing the wetting behavior of Pb-Sn perovskite precursor ink on PEDOT:PSS. This optimized process facilitates the deposition of high-quality, void-free Pb-Sn perovskite films with uniform thickness over 8 cm of coating length using moderate (1.4 bar) N2 quenching. We achieved 20 % efficient narrow bandgap perovskite solar cells and mini-modules with 15.8 % active area efficiency on 15.9 cm2.
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