Morphology and Photoluminescence of CH₃NH₃PbI₃ Deposits on Nonplanar, Strongly Curved Substrates

Abstract

Organic−inorganic metal halide perovskites have recently attracted increasing attention as highly efficient light harvesting materials for photovoltaic applications. The solution processability of these materials is one of their major advantages on the route toward fabrication of low-cost solar cells and optoelectronic devices. However, the precise control of crystallization and morphology of organometallic perovskites deposited from solutions, considered crucial for enhancing the final photovoltaic performance, still remains challenging. In this context, here, we report on growing microcrystalline deposits of methylammonium lead triiodide perovskite, CH3NH3PbI3 (MAPbI3), by one-step solution casting on cylinder-shaped quartz substrates (rods) having diameters in the range of 80 to 1800 μm. We show that the substrate curvature has a strong influence on morphology of the obtained polycrystalline deposits of MAPbI3. Specifically, a marked size reduction of MAPbI3 microcrystallites concomitant with an increased crystal packing density was observed with increasing the substrate curvatures. In contrast, although the crystallite 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 crystallite size reduction and a 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 (O2), nitrogen (N2), and argon (Ar). Specifically, under excitation with λexc = 546 nm, the rapid and pronounced decreases and increases of PL signals were observed under intermittent subsequent exposures to O2 and N2, respectively. 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.

Light-induced charge transfer at the CH3NH3PbI3/TiO2 interface—a low-temperature photo-electron paramagnetic resonance assay

“…It is noteworthy to mention that thin-film deposits of MAPbI 3 coated by single-step solution casting from neat DMF solutions very often appear to show microwire-or fibre-like surface morphology [51]. We also have previously reported similar microwire-like morphology and practically identical luminescence characteristics for single-step solution cast deposits of MAPbI 3 on various types of both curved and flat substrates (microwires with sizes of ∼8 μm in diameter and up to ∼150 μm in length were observed for small substrates' curvatures or flat surfaces) [52]. Therefore, one can conclude that the presence of blue-TiO 2 NWs does not significantly modify nucleation and crystal growth of MAPbI 3 microwires during deposition of the MAPbI 3 /blue-TiO 2 NWs nanohybrid from stoichiometric solutions of MAPbI 3 in DMF (for more details see section 2 and supplementary material, available online atstacks.iop.org/JPPHOTON/2/014007/mmedia).…”

Achieving High‐Performance Perovskite Photovoltaic by Morphology Engineering of Low‐Temperature Processed Zn‐Doped TiO2 Electron Transport Layer

“…Many research groups dedicated to investigating the relationship between those two, and it was reported that a structured substrate can facilitate the growth of compact and continuous perovskite thin film. [20][21][22][23][24][25] Here in our research, we proposed a two-fluid spray coating technique, combined with volatile ink solution and preheated substrate ( Figure S1, Supporting Information), to fabricate a structured ETL composed of LT-TiO 2 NCs.…”

“…It has been mentioned that the mesostructured ETL can facilitate the extraction of electron. [20][21][22][23][24][25] Besides, the texture of substrate can significantly influence the crystallization process of perovskite layer during deposition. S. Liu group has declared that perovskite layer with increased crystallinity and surface coverage can be achieved via controlling the wettability between perovskite droplet and the substrate.…”

Facile Synthesis of Methylammonium Lead Iodide Perovskite with Controllable Morphologies with Enhanced Luminescence Performance

“…In recent years, researchers have attempted to prepare MAPbI 3 nanocrystals with different morphologies, including zero-dimension (0D) nanodots, one-dimensional (1D) nanowires, nanorods, and nanobelts, 2D nanoplates, and three-dimensional (3D) nanocubes, by different preparation methods, including the dissolution-recrystallization method [20], conventional deposition method [21], and solution phase method [22]. However, the morphology of the prepared MAPbI 3 nanocrystals are not uniform, with the coexistence of nanowires, nanorods, nanoplates, and nanobelts in the sample, which may reduce PL intensity and weaken light absorption, which will be detrimental to their application in nanodevices [23].…”