Figure 1: Growth of orientationally pure crystalline (OPC) films.
From: Pure crystal orientation and anisotropic charge transport in large-area hybrid perovskite films
(a) Schematic representation of the thermal-gradient-assisted directional crystallization process of a MAPbI3 perovskite. A solution is pulled at a constant velocity, V, through a thermal gradient, G, generated by local heating at T1. (b) Optical microscope image of the aligned OPC films of the perovskite and (c) the magnified image of the highlighted area in (b) (white square). (d) The intermediate stage of microarray growth in liquid films showing the secondary branches growing from the propagating main backbone. (e) Isotropically growing microarrays by homogeneous annealing of the substrate. Insets show the same sample at a lower magnification (upper right) and the direction of its growth (upper left). (f) Spherulitic dendrites generated by lowering concentration with small thermal gradient or homogeneous annealing. (g) Optical microscope image of directionally grown MAPbBr3 wires using the thermal gradient method.
