  Organic-inorganic metal halide perovskites have recently attracted increasing
attention as highly efficient light harvesting materials for photovoltaic
applications. However, the precise control of crystallization and morphology of
organometallic perovskites deposited from solution, considered crucial for
enhancing the final photovoltaic performance, remains challenging. In this
context, here, we report on growing microcrystalline deposits of CH3NH3PbI3
(MAPbI3), by one-step solution casting on cylinde-shaped quartz substrates
(rods). We show that the substrate curvature has a strong influence on
morphology of the obtained polycrystalline deposits of MAPbI3. Although the
crystalline width and length markedly decreased for substrates with higher
curvatures, the photoluminescence (PL) spectral peak positions did not
significantly evolve for MAPbI3 deposits on substrates with different
diameters. The crystalline size reduction and denser coverage of
microcrystalline MAPbI3 deposits on cylinder-shaped substrates with higher
curvatures were attributed to two major contributions, both related to the
annealing step of the MAPbI3 deposits. In particular, the diameter-dependent
variability of the heat capacities and the substrate curvature-enhanced solvent
evaporation rate seemed to contribute the most to the crystallization process
and the resulting morphology changes of MAPbI3 deposits on cylinder-shaped
quartz substrates with various diameters. The longitudinal geometry of
cylinder-shaped substrates provided also a facile solution for checking the PL
response of the deposits of MAPbI3 exposed to the flow of various gaseous
media, such as oxygen, nitrogen and argon. Overall, the approach reported
herein inspires novel, cylinder-shaped geometries of MAPbI3 deposits, which can
find applications in low-cost photo-optical devices, including gas sensors.
