Phase-pure MAPbBr3 thin films prepared by room-temperature powder aerosol deposition (PAD) and their optical and electrical properties
摘要
Preparing MAPbBr3 films with thicknesses beyond a few micrometers remains challenging because solution-based deposition—particularly when multiple coating steps are required—can induce solvent-related film cracking and defects, while thermal exposure can accelerate degradation and compromise phase integrity. Here, we demonstrate that room-temperature powder aerosol deposition (PAD) enables the fabrication of dense, mechanically consolidated methylammonium lead bromide (MAPbBr3) films with thicknesses ranging from several micrometers up to several tens of micrometers. The high-velocity particle impact inherent to PAD does not compromise phase purity or crystal structure; instead, the deposited particles fracture into nanocrystallites (~ 90 nm) exhibiting low microstrain. Optical characterization confirms that the bandgap (~ 2.3 eV) remains unchanged relative to the precursor powder, demonstrating that the electronic structure remains largely preserved during the aerosol deposition process. Temperature-dependent impedance spectroscopy (293–383 K) reveals thermally activated ionic transport with activation energies of 0.55–0.59 eV, consistent with bromide vacancy formation and migration. Analysis of the dielectric loss tangent within the Trukhan framework gives an ionic diffusion coefficient of 3.1 × 10−8 cm2 s−1, an ionic mobility of 1.2 × 10−6 cm2 V−1 s−1 , and a mobile ion concentration of 2.6 × 1016 cm−3 at 293 K. This study establishes the first systematic investigation of ionic transport in PAD halide perovskite films, providing insight into bulk ion migration and the associated electrode interfacial polarization.