Electrochemical Deposition of Organometallic Halide Perovskite Single-Crystal Particles with Density Gradients and Their Stability, Fluorescence, and Photoelectrochemical Properties

Organometallic halide perovskites have gained immense scientific interest because of their unique optoelectronic properties that can benefit applications such as solar cells, lasers, and light-emitting diodes. Here, we develop a facile method to form a density gradient of MAPbI(3) (MA = methylammonium) crystal particles as a function of the electrochemical potential gradient across an indium-doped tin oxide (ITO) electrode. At the high-potential end of the ITO, a high density of nucleation sites is formed, yielding high-density MAPbI(3) crystals with a broad particle size distribution. Less density of MAPbI(3) crystals can be optically resolved at the low-potential end of the ITO. Spatial distributions of fluorescence and photoelectrochemical properties of the perovskite films show the same clear trends as the particle density gradients. Mass spectrum imaging of PbO2 and MAPbI(3) gradients shows a spatial distribution of PbO2, MAPbI(3) of fresh sample and PbI2 for aged sample. Mass spectrum imaging also reveals a poor structural stability of MAPbI(3) crystals formed at the high-potential side of the gradient because of their fast growth kinetics producing smaller nucleation sites.