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

A novel spacer cation, cystamine dihydrochloride, is employed to build DJ 2D/3D perovskites. It regulates crystal orientation and reduces residual strain in perovskite. The champion device achieves an efficiency of 24.54% with excellent stability.