Near-Room-Temperature Tunable Dielectric Response Induced by Dual Phase Transitions in a Lead-Free Hybrid: (C3H8N)2SbBr5
Organic-inorganic hybrid materials, which exhibit structural divrersity and rich physical properties, have shown great potentials as the basic device elements in the optoelectronic field. Herein, we report a new lead-free organic-inorganic hybrid, [C3H8N]2SbBr5 (1, where C3H8N+ is cyclopropylaminium cation), which adopts the one-dimensional (1D) zig-zag inorganic framewok consisting of the SbBr6 octahedra. Interestingly, 1 demonstrates tunable dielectric responses near the room temperature, derived from its two successive structural phase transitions at the vicinity of T1 = 285 K and T2= 315 K, respectively. That is, its dielectric constants change from high-dielectric (above T2), moderate-dielectric (between T2 and T1) and low-dielectric states (below T1). Such dielectric behaviors coincide well with a series of reversible thermal peaks in the DSC curve. Further structural analyses reveal that the dynamics of cyclopropylamine organic cations provides the driving force to bi-step phase transitions of 1 (i.e. order-disorder transformation). Moreover, theoretical calculation of electronic band structure of 1 reveals the direct feature with the band-gap value of ~2.36 eV. This work affords a broader design flexibility for the future exploration of electric-ordered materials in the organic-inorganic hybrid family.