Donor/Acceptor Charge-Transfer States at Two-Dimensional Metal Halide Perovskite and Organic Semiconductor Interfaces

Zhao, Lianfeng; Lin, Yuehe; Kim, Hoyeon; Giebink, Noel C.; Rand, Barry P.

doi:10.1021/acsenergylett.8b01722

Cited by 40 publications

(37 citation statements)

References 23 publications

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“…27 The organic layer determines other properties of the hybrid 2DLP as well, such as its hydrophobicity and stability; 21,[28][29] structural rigidity; 20,30 sheetto-sheet distance; [31][32][33] and the dielectric screening experienced by charge carriers confined within the inorganic layer. [34][35][36] Early work focused primarily on n = 1 layered perovskites, in which the alternating stacks of organic cations surround atomically-thin inorganic sheets. 3,9,[37][38][39][40] However, recent work has extensively centered on variable well thickness in layered structures with n > 1, in particular the Ruddlesden-Popper-phase perovskites (RPPs, Figure 2a).…”

Section: Structural Diversity In Hybrid Materialsmentioning

confidence: 99%

Excitons in 2D Organic–Inorganic Halide Perovskites

Mauck

Tisdale

2019

Trends in Chemistry

161

172

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Layered perovskites are hybrid two-dimensional materials, formed through the self-assembly of inorganic lead halide networks separated by organic ammonium cation layers. In these natural quantum-well structures, quantum and dielectric confinement lead to strongly bound excitonic states that depend sensitively on the material composition. In this article, we review current understanding of exciton photophysics in layered perovskites and highlight the many ways in which their excitonic properties can be tuned. In particular, we focus on the coupling of exciton dynamics to lattice motion and local distortions of the soft and deformable hybrid lattice. These effects lead to complex excited-state dynamics, presenting new opportunities for design of optoelectronic materials and exploration of fundamental photophysics in quantum confined systems.

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Section: Structural Diversity In Hybrid Materialsmentioning

confidence: 99%

Excitons in 2D Organic–Inorganic Halide Perovskites

Mauck

Tisdale

2019

Trends in Chemistry

161

172

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“…(19,27) This finding would instead support type-I alignment between RDPs of increasing n. Furthermore, in alignment with this framework, Silver et al recently investigated the IE and EA of BTA n = 1 films by a mix of experimental and computational studies with the conclusion that n = 1 exhibits type-I alignment with MAPbX3 bulk perovskite. (22) These conflicting reports of type-I and type-II band alignments among RDPs have propagated in citing literature, leading to contradictory explanations for optoelectronic device performance across the perovskite research community, some attributing their performance to type-I alignments, (19,28,29) some attributing it to type-II alignments, (30−32) and some speculating that their devices are pure phase making RDP interfaces irrelevant. (3) One source of inconsistency in RDP band alignment studies could be attributed to film inhomogeneity.…”

Section: Single-crystal Band Levelsmentioning

confidence: 99%

Ligand-Induced Surface Charge Density Modulation Generates Local Type-II Band Alignment in Reduced-Dimensional Perovskites

et al. 2019

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Two-dimensional (2D) and quasi-2D perovskite materials have enabled advances in device performance and stability relevant to a number of optoelectronic applications. However, the alignment among the bands of these variably quantum confined materials remains a controversial topic: there exist multiple experimental reports supporting type-I, and also others supporting type-II, band alignment among the reduceddimensional grains. Here we report a combined computational and experimental study showing that variable ligand concentration on grain surfaces modulates the surface charge density among neighboring quantum wells. Density functional theory calculations and ultraviolet photoelectron spectroscopy reveal that the effective work function of a given quantum well can be varied by modulating the density of ligands at the interface. These induce type-II interfaces in otherwise type-I aligned materials. By treating 2D perovskite films, we find that the effective work function can indeed be shifted down by up to 1 eV. We corroborate the model via a suite of pump−probe transient absorption experiments: these manifest charge transfer consistent with a modulation in band alignment of at least 200 meV among neighboring grains. The findings shed light on perovskite 2D band alignment and explain contrasting behavior of quasi-2D materials in light-emitting diodes (LEDs) and photovoltaics (PV) in the literature, where materials can exhibit either type-I or type-II interfaces depending on the ligand concentration at neighboring surfaces.

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“…This, in turn, results in a higher dielectric constant and reduces the exciton binding energy. [47,[75][76][77] This original approach opens a new way toward tailoring the optoelectronic properties of LPKs by using commercially available small dopants and the great variety of existing organic spacers. In the pioneering work by Passarelli et al a small organic electron-acceptor molecule, tetrachloro-1,2-benzoquinone TCBQ, was introduced to the organic layer formed by the naphthalene-based ammonium cations (Nap-O-R, R = ethylammonium, propylammonium, butylammonium, hexylammonium).…”

Section: Lead Halide Bond Distortionmentioning

confidence: 99%

Layered Perovskites in Solar Cells: Structure, Optoelectronic Properties, and Device Design

Sirbu

Balogun

Milot

et al. 2021

Advanced Energy Materials

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optoelectronic properties akin to industrial juggernauts gallium arsenide and silicon. [1,2] Yet, the materials are compatible with solution-processing techniques such as inkjet printing and spray coating. [3] This unprecedented combination has led to the development of solar cells which already show power conversion efficiencies of over 25%, similar to state-of-the-art poly-Si and other thin-film technologies, in just over 10 years of development. [4] Hybrid perovskites are particularly interesting for indoor applications, with impressive efficiencies of over 35% demonstrated under indoor illumination which may prove a viable option to power the ever expanding Internet of Things. [5] Rather than competing with the current technology giants, perovskites can work together with other solar cell technologies in a tandem configuration. Record efficiencies of over 29% for silicon-perovskite tandem solar cells have already been reported and further progress is expected in the near future. [6] Although perovskite solar cells (PSCs) are on the verge of mass production, two main challenges remain: stability [7] and toxicity. [8] Multiple reviews already address the toxicity concern, and it will not be discussed here. [9][10][11] Layered hybrid perovskites (LPKs) have emerged as an answer to battle stability concerns. Although known for decades, LPKs have only recently been incorporated in photovoltaic (PV) applications, resulting in modest device power conversion efficiencies due to poorer optoelectronic properties. [12][13][14] However, their key advantage is the stabilizing effects of the organic interlayers, which prevents perovskite degradation. [15,16] The organic spacer inhibits ion migration which prevents the formation of irreversible degradation products. [17] Alternatively, LPKs can be deposited over the state-of-the-art perovskite materials to combine the high performance of 3D perovskites with the stabilizing properties of LPKs. [15] Here, the limiting factor is inefficient charge transport across the organic interlayer, currently preventing the full exploitation of the layered structure in PSCs.This can be approached in two ways, either by keeping the LPK layer very thin, currently the most popular approach, or by increasing the electrical conductivity of the material. [18,19] The conductivity can be enhanced through increasing the number of inorganic layers n, but this comes at the price of reduced stability. [20][21][22] The better approach is to enhance the charge transport in LPKs through the molecular engineering of the organic Layered hybrid perovskites (LPKs) have emerged as a viable solution to address perovskite stability concerns and enable their implementation in wide-scale energy harvesting. Yet, although more stable, the performance of devices incorporating LPKs still lags behind that of state-of-the-art, multication perovskite materials. This is typically assigned to their poor charge transport, currently caused by the choice of cations used within the organic layer. On balance, a compromise bet...

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Donor/Acceptor Charge-Transfer States at Two-Dimensional Metal Halide Perovskite and Organic Semiconductor Interfaces

Cited by 40 publications

References 23 publications

Excitons in 2D Organic–Inorganic Halide Perovskites

Excitons in 2D Organic–Inorganic Halide Perovskites

Ligand-Induced Surface Charge Density Modulation Generates Local Type-II Band Alignment in Reduced-Dimensional Perovskites

Layered Perovskites in Solar Cells: Structure, Optoelectronic Properties, and Device Design

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