Controlled growth of MAPbBr3 single crystal: understanding the growth morphologies of vicinal hillocks on (100) facet to form perfect cubes

Abstract

Organic and inorganic hybrid perovskites have attracted significant attentions due to their impressive optoelectronic properties. MAPbBr 3 , one of the most popular members in MAPbX 3 (MA = methyl ammonium and X = Cl, Br, I) family, is considered as new generation optoelectronic materials, especially in the field of solar cells. Compared to polycrystalline films, MAPbBr 3 single crystal is deemed more ideal for optoelectronic device because of fewer grain boundaries. To realize a controlled crystal growth, a thorough understanding of its growth mechanism, especially the role of surface structures played in growth kinetics, is of paramount importance. In this paper, hillocks on (100) facet of MAPbBr 3 crystal were observed using atomic force microscopy when grown from N-dimethylformamide (DMF) solution. The results revealed that the growth of (100) facet was controlled by 2D nucleation at low concentration, which derived plenty of elementary steps whose height was about 0.59 nm, equivalent to one unit cell. Then the growth transferred to step flow model along [011] direction.Step flow ceased when encountering holes on the terraces. The optical morphologies validated that cubic plates were prone to growing along [011] directions, which were in a layer-by-layer model. Moreover, the temperature reverse solubility of MAPbBr 3 in DMF solution was measured. In terms of the solubility and growth mechanism of MAPbBr 3 , a series of MAPbBr 3 single crystals were successfully grown from thin cubic plates to thick and perfect cubes via temperature controlling rising method ultimately.

Organic‐Inorganic Hybrid Perovskite Single Crystals: Crystallization, Molecular Structures, and Bandgap Engineering

“…For example, as shown in Fig-ure 2a, the solubility of MAPbBr 3 in DMF decrease as the temperature of the solution increases. [49] First, the PbX 2 (X=Cl, Br, I) and CH 3 NH 3 X (X=Cl, Br, I) are added into these particular solvents and the solution is stirred with a magnetic stirrer at room temperature. After the solution is changed to be clear enough, the temperature of the solution is increased into1 00°C.…”

“…The widely used particular solvents are g‐butyrolactone (GBL), N, N′‐dimethylformamide (DMF) and dimethylsulphoxide (DMSO). For example, as shown in Figure a, the solubility of MAPbBr 3 in DMF decrease as the temperature of the solution increases . First, the PbX 2 (X=Cl, Br, I) and CH 3 NH 3 X (X=Cl, Br, I) are added into these particular solvents and the solution is stirred with a magnetic stirrer at room temperature.…”

“…a) Temperature dependence of solubility curve of MAPbBr 3 in DMF. Adapted with permission from Ref [49]…”

A 1300 mm2 Ultrahigh‐Performance Digital Imaging Assembly using High‐Quality Perovskite Single Crystals

“…Indeed, we have attained much improved crystalline quality as confirmed by X‐ray diffraction (XRD) analysis. More specifically, powder XRD (Figure c) shows very sharp peaks at 14.92°, 21.11°, 30.07°, 33.71°, 37.11°, 43.05°, and 45.77°, corresponding to the (001), (110), (002), (210), (211), (220), and (003) planes of the cubic MAPbBr 3 crystal structure, respectively . Furthermore, the X‐ray 2θ scan on the maximal facet of a typical MAPbBr 3 single crystal shows only (001), (002), (003), and (004) diffraction peaks, suggesting well‐structured single‐crystalline eminence (Figure d).…”

“…Compared with image obtained using the microcrystalline perovskite thin film (Figure S6c,d, Supporting Information), the present images exhibit much higher recognition due to much better uniformity of the sensor pixels and photocurrent response, thanks to the superior quality achieved using the LTGC single crystal. Furthermore, the response speed ( t rise = 43 µs and t decay = 36 µs) attained using the single‐crystal perovskite is not only much faster than the human‐eye pattern recognition (>40 ms), it is significantly faster than those state‐of‐the‐art devices achieved using the perovskite NWs ( t rise = 20.47 ms and t decay = 13.81 ms) . More comparison with other materials are summarized in Table S8 (Supporting Information).…”