Polar Solvent Induced Lattice Distortion of Cubic CsPbI Nanocubes and Hierarchical Self-Assembly into Orthorhombic Single-Crystalline Nanowires.

Despite the recent surge of interest in inorganic lead halide perovskite nanocrystals, there are still significant gaps in their stability disturbance and the understanding of their destabilization, assembly, and growth processes. Here, we discover that polar solvent molecules can induce the lattice distortion of ligand-stabilized cubic CsPbI, leading to the phase transition into orthorhombic phase, which is unfavorable for photovoltaic applications. Such lattice distortion triggers the dipole moment on CsPbI nanocubes, which subsequently initiates the hierarchical self-assembly of CsPbI nanocubes into single-crystalline nanowires. The systematic investigations and in situ monitoring on the kinetics of the self-assembly process disclose that the more amount or the stronger polarity of solvent can induce the more rapid self-assembly and phase transition. These results not only elucidate the destabilization mechanism of cubic CsPbI nanocrystals, but also open up opportunities to synthesize and store cubic CsPbI for their practical applications in photovoltaics and optoelectronics.