The field of metal halide perovskites has experienced unprecedented expansion in the last 10 years. These materials have the potential to establish a new generation of optoelectronics devices contributing to the mitigation routes for problems such as global warming. However, this technology is facing important challenges which hinder its tangible impact on the final applications, with performance and stability being critical limiting parameters. Metal halide perovskite macro and nanocrystals can provide crucial tools to tackle the current difficulties, yet the working mechanisms of these structures can differ significantly from conventional polycrystalline thin-films ones. We present new synthesis and passivation methods to fabricate device-oriented perovskite structures, including monocrystals in the macro and nanoscale. We study the physical processes and their impact on different applications such as photovoltaics and neuromorphic circuit components. From the electrical perspective, we develop an impedance spectroscopy model adapting the phase dispersion as a function of the ionic modulation.