Organolead halide perovskites with the general formula CH₃NH₃PbX₃ (X = Cl, Br, I) receive great attention in the field of light energy conversion due to their high absorption coefficient at visible wavelengths and a long-range electron-hole diffusion. Perovskite-based solar cells consist of a thin perovskite layer deposited between conductive scaffolds. So far, the best devices exhibit photovoltaic performances with power conversion efficiencies up to 20%.^1,2 Controlling the crystallinity and morphology of the perovkite layer is crucial for tuning the optical properties as well as for improving the performance of the devices.^3,4

Besides the preparation of a continuous perovskite film for solar cells, few reports describe the fabrication of low-dimensional organolead halide crystals. Isolated perovskite particles represent the prototype for fundamental research on the underlying intrinsic properties, while thin films often display inhomogeneities and low stability. Hence, exploiting new solution-processed preparation methods in order to get uniform single crystals for potentially more efficient crystalline perovskite-based solar devices, is desirable. Reports describe the generation of perovskite particles with different morphologies and shape-dependent optical properties by adjusting the polarities of the solvents or adding varying concentrations of bulky organic cations.^5,6 Recently, synthetic approaches have been reported for the fabrication of very bright luminescent colloidal perovskite suspensions by adding a varying amount of long-chain surface capping ligands and organic acids. Perovskite nanowires, rods and quantum dot-like particles with a high colloidal stability have been obtained. However, the main drawback is the size- and shape inhomogeneity among different samples.^7-9

Here, the morphogy controlled fabrication of organolead halide perovskites with a narrow size distrubution will be presented. Upon checking the morphology by SEM, single-particle fluorescence microscopy measurements are carried out in a correlated way to obtain a deeper insight into the photoluminescence performance of the perovskite nanocrystals. Furthermore, the stability according to their structural geometry, chemical composition and photophysical properties is compared with previously prepared perovskite planar films.¹⁰

1 Zhou et al. Science, 2014, 345, 542

2 Heo et al. Nature Photonics, 2013, 7, 487

3 Bi et al. ACS Appl. Mat. Interfaces, 2014, 6, 18751

4 Yang et al. Chem. Mater., 2014, 26, 6705

5 Chen et al. Mater. Res. Express, 2014, 1, 015034

6 Zhu et al. ACS Nano, 2015, 9, 2948   

7 Pathak et al. Chem. Mater., 2015, 27, 8066

8 Zhang et al. ACS Nano, 2015, 9, 4533

9 Vybornyi et al. Nanoscale, 2016

10 Yuan, Debroye et al. J. Phys. Chem. Lett., 2016, 7, 561