Excitonics in<scp>2D</scp>Perovskites

Chong, Wee Kiang; Giovanni, David; Sum, Tze-Chien

doi:10.1002/9783527800766.ch1_03

Cited by 7 publications

(7 citation statements)

References 76 publications

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“…This is because their reduced dimensionality manifestsi npoor charge transport and compromised visible light absorption. [26,27] The former results from strongly bound electron-hole pairs (excitons) and is quantified by the exciton binding energy (E b ). The latter can be traced to the comparatively high energy of the excitonic transitions of 2D iodoplumbates, which range from 468 to 518 nm and equatet ob and gap energies (E g ) > 2.45 eV.…”

Section: Introductionmentioning

confidence: 99%

Molecular Engineering of Pure 2D Lead‐Iodide Perovskite Solar Absorbers Displaying Reduced Band Gaps and Dielectric Confinement

et al. 2020

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Section: Introductionmentioning

confidence: 99%

Molecular Engineering of Pure 2D Lead‐Iodide Perovskite Solar Absorbers Displaying Reduced Band Gaps and Dielectric Confinement

et al. 2020

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“…[39][40][41] The excitonic character of the excited state is accompanied by an effective widening of the bandgap, an increase in the oscillator strength, and a narrowing of the emission spectrum. [40][41][42] The strongest confinement effects are observed for n = 1, where the excited state is confined to a single B-X-octahedral layer (see Figure 1a). Light harvesting using 2D perovskites relies on the efficient transport of excitons and their subsequent separation into free charges.…”

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confidence: 99%

Exciton diffusion in two-dimensional metal-halide perovskites

et al. 2020

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Two-dimensional perovskites, in which inorganic layers are stabilized by organic spacer molecules, are attracting increasing attention as a more robust analogue to the conventional three-dimensional metal-halide perovskites. However, reducing the perovskite dimensionality alters their optoelectronic properties dramatically, yielding excited states that are dominated by bound electron-hole pairs known as excitons, rather than by free charge carriers common to their bulk counterparts. Despite the growing interest in two-dimensional perovskites for both light harvesting and light emitting applications, the full impact of the excitonic nature on their optoelectronic properties remains unclear, particularly regarding the spatial dynamics of the excitons within the two-dimensional (2D) plane.Here, we present direct measurements of in-plane exciton transport in single-crystalline layered perovskites. Using time-resolved fluorescence microscopy, we show that excitons undergo an initial fast, intrinsic normal diffusion through the crystalline plane, followed by a transition to a slower subdiffusive regime as excitons get trapped. Interestingly, the early intrinsic exciton diffusivity depends sensitively on the choice of organic spacer. We find a clear correlation between the stiffness of the lattice and the diffusivity, suggesting exciton-phonon interactions to be dominant in determining the spatial dynamics of the excitons in these materials. Our findings provide a clear design strategy to optimize exciton transport in these systems. lead, tin), X is a halide anion (chloride, bromide, iodide), L is a long organic spacer molecule, and n is the number of octahedra that make up the thickness of the inorganic layer. The separation into fewatom thick inorganic layers yields strong quantum and dielectric confinement effects. 38 As a result, the exciton binding energies in 2D perovskites can be as high as several hundreds of meVs, which is around an order of magnitude larger than those found in bulk perovskites. [39][40][41] The excitonic character of the excited state is accompanied by an effective widening of the bandgap, an increase in the oscillator strength, and a narrowing of the emission spectrum. [40][41][42] The strongest confinement effects are observed for n = 1, where the excited state is confined to a single B-X-octahedral layer (see Figure 1a).Light harvesting using 2D perovskites relies on the efficient transport of excitons and their subsequent separation into free charges. 43 This stands in contrast to bulk perovskites in which free charges are generated instantaneously thanks to the small exciton binding energy. 39 Particularly, with excitons being neutral quasi-particles, the charge extraction becomes significantly more challenging as they cannot be guided to the electrodes through an external electric field. 44 Excitons need to diffuse to an interface before the electron and hole can be efficiently separated into free charges. 45 On the other hand, for light emitting applications the spatial displacement is ...

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“…[11,12] Indeed, these 2D systems have already been demonstrated to possess several unique properties such as moisture stability,t hermal stability,s elf-trapping of excitonic features,a nd long carrier lifetimes.T hese properties make them highly applicable for LEDs,lasing, and white-light emission applications as well. [13][14][15][16][17][18][19][20] The2Dlead based HOIPs (tolerance factor, t > 1) can form Ruddlesden Popper (RP) type phase (general formula:A n+1 B n X 3n+1 ), Dion-Jacobson type perovskite phase (general formula:A 'A nÀ1 Pb n X 3n+1 )o r alternating cation type phase (general formula: (A'A) n+1 B n X 3n+1 )b yi ncorporation of long alkyl/aryl-organic monovalent or divalent cations,respectively. [21] Also,insome cases some degree of strain is imparted to the MX 6 À octahedra from the organic cations,which leads to distorted octahedra, giving rise to some uniquely interesting electronic density of states and properties.M ao et al have reported ac orrugated 2D hybrid perovskite (DMEN)PbBr 4 (2-(Dimethylamino)ethylamine lead bromide), which exhibited broadband white light emission with an impressive colour rendering index (CRI) value of 73.…”

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An Organic–Inorganic Perovskitoid with Zwitterion Cysteamine Linker and its Crystal–Crystal Transformation to Ruddlesden‐Popper Phase

et al. 2021

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We demonstrate synthesis of an ew low-D hybrid perovskitoid (a perovskite-like hybrid halide structure,y ellow crystals,P 21/n space group) using zwitterion cysteamine (2aminoethanethiol) linker,a nd its remarkable molecular diffusion-controlled crystal-to-crystal transformation to Ruddlesden-Popper phase (Red crystals,P nma space group). Our stable intermediate perovskitoid distinctly differs from all previous reports by way of aunique staggered arrangement of holes in the puckered 2D configuration with af ace-sharing connection between the corrugated-1D double chains.The PL intensity for the yellowphase is 5orders higher as compared to the red phase and the corresponding average lifetime is also fairly long (143 ns). First principles DFT calculations conform very well with the experimental band gap data. We demonstrate applicability of the new perovskitoid yellow phase as an excellent active layer in as elf-powered photodetector and for selective detection of Ni 2+ via On-Off-On photoluminescence (PL) based on its composite with few-layer black phosphorous.

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Excitonics in2DPerovskites

Cited by 7 publications

References 76 publications

Molecular Engineering of Pure 2D Lead‐Iodide Perovskite Solar Absorbers Displaying Reduced Band Gaps and Dielectric Confinement

Molecular Engineering of Pure 2D Lead‐Iodide Perovskite Solar Absorbers Displaying Reduced Band Gaps and Dielectric Confinement

Exciton diffusion in two-dimensional metal-halide perovskites

An Organic–Inorganic Perovskitoid with Zwitterion Cysteamine Linker and its Crystal–Crystal Transformation to Ruddlesden‐Popper Phase

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