a Schematic illustration of RSM device using dimer-Cs3Sb2I9 deposited by a spin-coating process. b Schematic structure of dimer-Cs3Sb2I9 (atom colors: Cs = blue-green; Sb = purple; I = brown). The rectangular box in schematic structure is the unit cell of crystal structure. c Cross-sectional scanning-electron microscopy (SEM) image of dimer-Cs3Sb2I9 layer on ITO. d I–V characteristics of dimer-Cs3Sb2I9 RSM. e Data retention properties of the dimer-Cs3Sb2I9 RSM.