Inhibition of a structural phase transition in one-dimensional organometal halide perovskite nanorods grown inside porous silicon nanotube templates

Abstract

One-dimensional organo-metal halide Perovskite (CH 3 NH 3 PbI 3 ) nanorods whose diameter and length are dictated by the inner size of porous silicon nanotube templates have been grown, characterized and compared to bulk perovskites in the form of microwires. We have observed a structural phase transition for bulk perovskites, where the crystal structure changes from tetragonal to orthorhombic at about 150K, as opposed to small diameter one-dimensional perovskite nanorods, of the order of 30-70 nm in diameter, where the phase transition is inhibited and the dominant phase remains tetragonal. Two major experimental techniques, infrared absorption spectroscopy and photoluminescence, were utilized to probe the temperature dependence of the perovskite phases over the 4-300K temperature range.Yet, different characteristics of the phase transition were measured by the two spectroscopic methods and explained by the presence of small, tetragonal inclusions embedded in the orthorhombic phase. The inhibition of the phase transition is attributed to the large surface area of these one-dimensional perovskite nanorods, which gives rise to a large stress that, in turn, prevents the formation of the orthorhombic phase. The absence of phase transition enables the measurement of the tetragonal bandgap energy down to low temperatures. *

Structural effects on optoelectronic properties of halide perovskites

“…215,[220][221][222] Arad-Vosk et al undertook a very fundamental study on the temperature dependent phase transformation of CH 3 NH 3 PbI 3 nanorods. 221 Bulk MAPbI 3 undergoes a phase transition from the orthorhombic to the tetragonal phase when the temperature is increased above approximately 160 K. In contrast, small nanorods with diameters below 70 nm embedded in porous silicon do not undergo phase transition to the orthorhombic phase at low temperatures. As the diameter increases, nanorods with a larger diameter (175 nm) begin to resemble the properties of the bulk material.…”

“…Since the diameter, and therefore the surface to bulk ratio, was found to be significant for the stabilization of the tetragonal phase at lower temperatures, surface energy is likely to significantly contribute to the stabilization. 220,221 Halide perovskite nanowires of various compositions were also fabricated in an ordered array on transparent conductive substrates, which opens the route to halide perovskite nanowire array photovoltaics. Ashley et al prepared nanowires in a template of anodized aluminum oxide (AAO) on a conductive transparent substrate (Fig.…”

Investigating the Tetragonal‐to‐Orthorhombic Phase Transition of Methylammonium Lead Iodide Single Crystals by Detailed Photoluminescence Analysis

“…[ 4–7 ] Various parameters have been identified which can influence this phase transition, such as the exact stoichiometry of the perovskite [ 8 ] or external constraints. [ 9 ] Also, the phase transition was found to proceed differently with temperature, depending on whether a single crystal or a thin film is investigated. In the case of thin films, aspects such as strain, disorder or polycrystallinity were reported to play an important role in inhibiting the phase transition, i.e., it takes place at lower temperatures and/or over a wider temperature range.…”

Silicon‐Based Inorganic–Organic Hybrid Nanocomposites for Optoelectronic Applications

“…PbO was electrodeposited on both bare silicon and freshly prepared PS from an aqueous solutions of lead acetate (Pb(CH 3 COO) 2 (4 m m , Aldrich Chemicals) and sodium acetate (0.2 m ) at pH 5.0. Deposition of PbO into PS was carried out using a three‐electrode setup with the same Teflon cell mentioned above at an optimized potential of 2.3 V for times (40–200 s) required to achieve a certain film thickness . All PbO‐deposited samples (on bare silicon and/or PS) were converted into CHPI by direct intercalation of 2‐(1‐cyclohexenyl) ethylammonium iodide (C 6 H 9 C 2 H 4 NH 3 I, CHI,) into PbO, where a rapid iodination occurred inside the organic moiety, converting the nanocomposite into the desired CHPI.…”

“…The direct deposition and intercalation of organic moiety into layered host were also recently established . Recently, growth of 3D perovskite nanorods within an IR‐transparent nanoporous silicon template prepared using chemical vapor deposition (CVD) was reported . However, for complete space filling, growth, and nucleation on the nanoscale, electrochemical deposition is more suitable and very few reports are available because of fabrication issues .…”