Controlled crystal orientation and reduced lattice distortion with a cystamine dihydrochloride spacer for efficient and stable 2D/3D perovskite solar cells

Long-chain organic spacer diamine molecules are pivotal to the development of mixed two-dimensional (2D) and three-dimensional (3D) perovskites, as they integrate the enhanced stability of 2D perovskites with exceptional efficiency of 3D perovskites. Despite their potential, research on incorporating Dion-Jacobson (DJ) 2D components into the two-step fabrication process of 2D/3D perovskites and the effect of organic spacer diamine molecules on crystal orientation and lattice distortion remains insufficient. Herein, a novel organic spacer diamine molecule, cystamine dihydrochloride (CysCl), has been introduced to construct DJ 2D/3D perovskites. The resulting DJ 2D perovskite enables the development of high-quality perovskite films with improved crystal alignment, reduced lattice distortion, alleviated residual stress, and enhanced carrier transport. Consequently, the DJ 2D/3D device achieves an impressive efficiency of 24.54%, outperforming the control 3D perovskite device (22.72%). Notably, the non-encapsulated device retains 86% of its original efficiency after 1400 hours of continuous exposure to AM 1.5G light under ambient air conditions (25 +/- 5 degrees C and 50 +/- 5% relative humidity). Additionally, it demonstrates negligible degradation after 675 hours under combined thermal and light stress, meeting the ISOS-L-2 standard.