Lead halide perovskites (LHP) are of interest for light-emitting applications due to the tunability of their bandgap across the visible and near-infrared spectrum (IR) coupled with efficient photoluminescence quantum yields (PLQY). It is widely speculated that photoexcited electrons and holes spatially separate into large negative (electron) and positive (hole) polarons. Polarons are expected to be optically active. With the observed optoelectronic signatures expecting to show potential excited states within the polaronic potential well. From the polaron excited-state we predict that large polarons should be capable of spontaneous emission, photoluminescence, in the mid-IR to far-IR regime based on the concept of inverse occupations within the polaron potential well. Here we use density functional theory (DFT), including spin–orbit coupling interactions, for calculations on a two-dimensional Dion-Jacobson (DJ) lead chloride perovskite atomistic model of various sizes as a host material for either negative or positive polarons to examine the effects of size on polaron formation. This work provides computational evidence that polaron formation through selective charge injection does not show the same level of localisation for positive and negative polarons.
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Role of perovskite thickness on optoelectronic properties in lead bromide and lead iodide thin film perovskites: A DFT study
Two-dimensional organic–inorganic hybrid lead halide perovskites are of interest for photovoltaic and light emitting devices due to their favorable properties that can be tuned. Here we use density functional theory to model two-dimensional lead halide perovskites of different thicknesses and using two different hallogens. Excited-state optoelectronic properties of the perovskite models are examined using excited-state dynamics treated by reduced density matrix method. Nonadiabatic couplings were computed based on the on-the-fly approach along a molecular dynamics trajectory at ambient temperatures. The density matrix-based equation of motion for electronic degrees of freedom was used to determine the dynamics of electronic degrees of freedom. We observe that the thickness of the perovskite layer shows a redshift in the absorption spectra with increasing thickness but has minimal effect on the photoluminescence quantum yield of the material.
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- PAR ID:
- 10528766
- Publisher / Repository:
- Materials Research Society
- Date Published:
- Journal Name:
- MRS Advances
- Volume:
- 8
- Issue:
- 16
- ISSN:
- 2059-8521
- Page Range / eLocation ID:
- 901 to 906
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Lead halide perovskites are promising materials for a range of applications owing to their unique crystal structure and optoelectronic properties. Understanding the relationship between the atomic/mesostructures and the associated properties of perovskite materials is crucial to their application performances. Herein, the detailed pressure processing of CsPbBr3perovskite nanocube superlattices (NC‐SLs) is reported for the first time. By using in situ synchrotron‐based small/wide angle X‐ray scattering and photoluminescence (PL) probes, the NC‐SL structural transformations are correlated at both atomic and mesoscale levels with the band‐gap evolution through a pressure cycle of 0 ↔ 17.5 GPa. After the pressurization, the individual CsPbBr3NCs fuse into 2D nanoplatelets (NPLs) with a uniform thickness. The pressure‐synthesized perovskite NPLs exhibit a single cubic crystal structure, a 1.6‐fold enhanced photoluminescence quantum yield, and a longer emission lifetime than the starting NCs. This study demonstrates that pressure processing can serve as a novel approach for the rapid conversion of lead halide perovskites into structures with enhanced properties.
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Hybrid organic–inorganic perovskites (HOIPs) have become an important class of semiconductors for solar cells and other optoelectronic applications. Electron–phonon coupling plays a critical role in all optoelectronic devices, and although the lattice dynamics and phonon frequencies of HOIPs have been well studied, little attention has been given to phonon lifetimes. We report high-precision momentum-resolved measurements of acoustic phonon lifetimes in the hybrid perovskite methylammonium lead iodide (MAPI), using inelastic neutron spectroscopy to provide high-energy resolution and fully deuterated single crystals to reduce incoherent scattering from hydrogen. Our measurements reveal extremely short lifetimes on the order of picoseconds, corresponding to nanometer mean free paths and demonstrating that acoustic phonons are unable to dissipate heat efficiently. Lattice-dynamics calculations using ab initio third-order perturbation theory indicate that the short lifetimes stem from strong three-phonon interactions and a high density of low-energy optical phonon modes related to the degrees of freedom of the organic cation. Such short lifetimes have significant implications for electron–phonon coupling in MAPI and other HOIPs, with direct impacts on optoelectronic devices both in the cooling of hot carriers and in the transport and recombination of band edge carriers. These findings illustrate a fundamental difference between HOIPs and conventional photovoltaic semiconductors and demonstrate the importance of understanding lattice dynamics in the effort to develop metal halide perovskite optoelectronic devices.
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Abstract Halide perovskites have attracted great interest as promising next‐generation materials in optoelectronics, ranging from solar cells to light‐emitting diodes. Despite their exceptional optoelectronic properties and low cost, the prototypical organic–inorganic hybrid lead halide perovskites suffer from toxicity and low stability. Therefore, it is of high demand to search for stable and nontoxic alternatives to the hybrid lead halide perovskites. Recently, high‐throughput computational materials design has emerged as a powerful approach to accelerate the discovery of new halide perovskite compositions or even novel compounds beyond perovskites. In this review, we discuss how this approach discovers halide perovskites and beyond for optoelectronics. We first overview the background of halide perovskites and methodologies in high‐throughput computational design. Then, we focus on materials properties for different optoelectronic applications, and how they are assessed with materials descriptors. Finally, we review different studies in terms of specific materials types to discuss their design principles, screening results, and experimental verification.
This article is categorized under:
Structure and Mechanism > Computational Materials Science
Electronic Structure Theory > Density Functional Theory
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Abstract Lead halide perovskites have recently emerged as promising absorbers for fabricating low‐cost and high‐efficiency thin‐film solar cells. The record power conversion efficiency of lead halide perovskite‐based solar cells has rapidly increased from 3.8% in 2009 to 22.1% in early 2016. Such rapid improvement is attributed to the superior and unique photovoltaic properties of lead halide perovskites, such as the extremely high optical absorption coefficients and super‐long photogenerated carrier lifetimes and diffusion lengths that are not seen in any other polycrystalline thin‐film solar cell materials. In the past a few years, theoretical approaches have been extensively applied to understand the fundamental mechanisms responsible for the superior photovoltaic properties of lead halide perovskites and have gained significant insights. This review article highlights the important theoretical results reported in literature for the understanding of the unique structural, electronic, optical, and defect properties of lead halide perovskite materials. For comparison, we also review the theoretical results reported in literature for some lead‐free perovskites, double perovskites, and nonperovskites.
- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1557/s43580-023-00641-y
