Regulating the crystallization of tin oxide nanoparticles by an environmentally friendly poly-aluminum chloride additive for a high-quality electron transport film in perovskite solar cells

Abstract

The film quality of the electron transport layers influences the photovoltaic performance of perovskite solar cells (PSCs) profoundly. Accordingly, we propose a green and cost-effective strategy for enhancing the optoelectrical properties of the tin oxide (SnO₂) layer by introducing polyaluminum chloride (PAC) as a precursor additive. By adding PAC to the SnO₂ nanoparticle precursor solution, the dispersion of nanoparticles is improved and the colloidal particle size is reduced. By adopting this strategy, the electrical conductivity of the SnO₂ film is improved significantly. This enhances the electron mobility of the PAC-modified SnO₂ film by almost threefold compared to the initial devices and leads to good charge extraction performance. Meanwhile, the energy level alignment between SnO₂ and the perovskite layers is optimized. Owing to the modification of the precursor solution with PAC, the power conversion efficiency (PCE) of the perovskite solar cells has been remarkably improved from 20.02% to 22.67%. Additionally, the PAC-modified devices without encapsulation retain 80% of their initial efficiency after aging at 85 °C in the dark for 160 hours, whereas only 69% was retained for the control device.