On the Shape-Selected, Ligand-Free Preparation of Hybrid Perovskite (CH3NH3PbBr3) Microcrystals and Their Suitability as Model-System for Single-Crystal Studies of Optoelectronic Properties

Abstract

Hybrid perovskite materials are one of the most promising candidates for optoelectronic applications, e.g., solar cells and LEDs, which can be produced at low cost compared to established materials. Although this field of research has seen a huge upsurge in the past decade, there is a major lack in understanding the underlying processes, such as shape-property relationships and the role of defects. Our aerosol-assisted synthesis pathway offers the possibility to obtain methylammonium lead bromide (MAPbBr3) microcrystals from a liquid single source precursor. The differently shaped particles are aligned on several substrates, without using a directing agent or other additives. The obtained particles show good stability under dry conditions. This allows us to characterize these materials and their pure surfaces at the single-crystal level using time- and spatially resolved methods, without any influences of size-dependent effects. By optimizing the precursor for the aerosol process, we were able to eliminate any purification steps and use the materials as processed. In addition, we performed theoretical simulations to deepen the understanding of the underlying processes in the formation of the different crystal facets and their specific properties. The model system presented provides insights into the shape-related properties of MAPbBr3 single crystals and their directed but ligand-free synthesis.

Microcrystals as amplifiers to learn about the facet- and point de-fect-dependent lability and stabilization of hybrid perovskite semi-conductors against humidity and light

“…The microcrystals were prepared by the aerosol assisted method as described in our previous publications. 28,29 Scanning electron microscopy (SEM) images of the as-prepared materials comprising cubic (CU) and rhombododecahedral (RD) microcrystals are shown in Fig. 1 and Supporting Information Fig.…”

“…The liquid precursors were synthesized according to the process we presented in an earlier work. 28,29 A 0.3 M solution of PbBr2 in a 1:1 (v:v) mixture of TEG and DMF was prepared and 1.0 eq MABr for rhombododecahedral (RD), respectively 1.8 eq for cubic (CU) microcrystals, was added. For the Cs substituted materials the liquid precursor was modified by the addition of 0.07 eq Cs + , compared to Pb 2+ .…”

“…The set-up used for this kind of synthesis was the same as reported in our latest work. 29 The aerosol of the liquid precursor was generated using a reservoir vessel equipped with a suction tube, connected with a model 3076 aerosol generator from TSI Inc. The aerosol was led through a tubular oven, using a 2 l/min nitrogen stream.…”

“…28 In our previous study we were successful in further improving our SSP, resulting in a precise control over the shape and crystal orientation of the single crystals obtained. 29 The obtained micrometer sized single crystals offered the opportunity to precisely characterize the optoelectronic properties with spatially and time-resolved methods. This led to a deepening in the understanding of the shape-property relationships of hybrid perovskite materials.…”

Aerosol-Prepared Microcrystals as Amplifiers to Learn about the Facet and Point Defect-Dependent Lability and Stabilization of Hybrid Perovskite Semiconductors against Humidity and Light

“…This adaption was inevitable to transfer the hybrid perovskite preparation to a unique, aerosol-assisted synthesis pathway that resulted in defined micrometer-sized crystals . In our previous study, we were successful in further improving our SSP, gaining precise control over the shape and crystal orientation of the single crystals obtained from this process . The micrometer-sized single crystals offered the opportunity to precisely characterize the optoelectronic properties with spatial- and time-resolved methods.…”