Bifunctional Effects of Trichloro(octyl)silane Modification on the Performance and Stability of a Perovskite Solar Cell via Microscopic Characterization Techniques

Passivation by small organic compounds can reduce the trap density and enhance the humidity and illumination stability of perovskite solar cells (PSCs). However, the small molecule passivated on the perovskite film cannot endure harsh heat stress. Herein, we find that the trichloro(octyl)silane (TC-silane) is an excellent candidate to modify the perovskite surface and grain boundary nondestructively through the formation of a heat-resistive silicone layer, leading to a comprehensive improvement of efficiency and stability with low cost as well as facile fabrication. The silane is a type of solvent and can be upscaled by a solution process in the device. TC-silicone can cross-link the grain boundaries through hydrolytic condensation. The cross-linking silicone can resist the moisture and heat stresses to enhance the stability. Also, microphotoluminescence reveals that TC-silane treatment can passivate the perovskite film and enhance the optoelectronic properties through chloride replenishment by releasing a hydrogen chloride molecule in the hydrolytic reaction. By utilizing Kevin probe force microscopy, we further uncover that TC-silane forms a dipole layer to facilitate the charge separation. TC-silane passivated PSCs deliver a champion efficiency of 20.03% and remain at 80% of their initial efficiency for more than 800 h at 70–80% relative humidity in air and for about 80 h under 85 °C thermal stress without encapsulation.