The MAPbBr3 crystals characterized in this work were grown following a modified inverse temperature crystallization (ITC) method reported in the literature. An illustration of the growth process is shown in Figure . A 1:1 molar ratio of PbBr2 and MABr was dissolved in DMF. The precursor solution was allowed to stir at room temperature for 24 hours to ensure that all starting materials dissolved. The precursor solution was then passed through a 0.2 μm PTFE syringe filter and added directly to a glass crystallizing dish on a hot plate. Small seed crystals were grown in an initial crystal growth step. Once the seeds had grown to an appreciable size for ease of handling (~1×1×0.5 mm), they were harvested from the growth solution and transferred to a separate glass crystallizing dish containing fresh precursor solution for seeded growth propagation. Seeded crystal growth was performed on a glass substrate placed at the bottom of the crystallizing dish to achieve a flat crystal surface at the glass-crystal interface. The growth was allowed to propagate for approximately five days uninterrupted. Once the growth was complete, a ~2.7×2.7×0.4 cm crystal (Figure ) was removed from the solution and dried with a Kimwipe prior to further analysis. Figure shows an illustration of the cubic MAPbBr3 unit cell where the gray spheres at the center of the octahedra represent Pb 2+ , the green spheres on the corners represent the halide (X -), and the blue sphere at the center of the unit cell is the organic cation (A + ).