Exciton and Free Charge Dynamics of Methylammonium Lead Iodide Perovskites Are Different in the Tetragonal and Orthorhombic Phases

Wang, He; Whittaker‐Brooks, Luisa; Fleming, Graham R.

doi:10.1021/acs.jpcc.5b04403

Cited by 67 publications

(83 citation statements)

References 33 publications

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“…[34,35] Within the vicinity of the transition temperature, spatially-resolved PL studies, as well as temperature-dependent XRD measurements, showed that both phases coexist [35,36] and that an energy transfer from the orthorhombic phase to tetragonal inclusions takes place on the picosecond time scale (70 ps). [37] The temperature-dependent changes in the photoluminescence spectra of MAPbI 3 were reported by numerous groups, for both thin films as well as their single crystal counterparts. [16,17,24,[33][34][35][38][39][40] The unusual blue shift in the transition region of the phase transition is, at present, not well understood.…”

Section: Photoluminescencementioning

confidence: 81%

Impact of Structural Dynamics on the Optical Properties of Methylammonium Lead Iodide Perovskites

Panzer

Meier

et al. 2017

Advanced Energy Materials

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structure, [2] and changing the ratio of precursor compounds prior to the formation of the perovskite layer. [3] These approaches are based on modifying the crystallization process, for example, by controlling the composition of the precursor solution and by varying processing parameters. Such changes also led to major improvements in perovskite-based light-emitting devices within the last year. Initially, the current efficiencies were improved by optimizing the grain size to values below 100 nm, and by changing the precursor compound molar proportions. [4] More recently, efficient perovskite-based LEDs with external quantum efficiencies exceeding 10% were even obtained by expanding towards lower dimensional perovskite structures. [5] Different structures and dimensionalities resulted in altered charge-carrier dynamics affecting the radiative recombination efficiency. [5,6] By drawing strong correlations between structural properties and their electronic structure, major breakthroughs toward light-emitting devices or in photovoltaics could be achieved in very recent years. To a certain extent, this resembles the evolution in the field of organic semiconductors, where improved understanding of the interplay between morphological and electronic structure proved essential to facilitate the recent progress in organic photovoltaics, and the successful commercialisation of organic LED devices. Also, for hybrid perovskites the question of how crystal structure, shape, and grain size governs the electronic structure will remain an important topic in the future to further improve perovskite-based optoelectronic devices. Since the solution processability of hybrid perovskites enables easy tuning of material compositions, a large number of different hybrid perovskites were reported. For example, exchanging the organic cation can alter the crystal structure, shift phase transitions, as does formamidinium, or change further excited-state dynamics, as is happening with Cs or Ru. Furthermore, different halide anions change the optical and excited state properties. The optical bandgap can be changed from the UV to NIR region by replacing the halide from Cl to Br to I. Mixed-halide systems thereof even provide a way to gradually tune the respective bandgap. In fact, the recently reported, most stable and efficient perovskite solar cells (PSCs) are based on a highly optimized mixture of different anions and cations. [1,7] Nevertheless, the most investigated hybrid perovskite representative is the methylammonium lead iodide perovskite CH 3 NH 3 PbI 3 (MAPbI 3 ), which, in the meantime, has become Organolead halide perovskites have attracted a lot of attention over the recent years mostly due to their bright prospective application in photovoltaic devices. For further development, characterization of their physical properties plays a seminal role in order to gain an in-depth understanding of these mid-bandgap ionic semiconductors. Their unique optical and electronic properties are a result of their characteristic electronic stru...

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Section: Photoluminescencementioning

confidence: 81%

Impact of Structural Dynamics on the Optical Properties of Methylammonium Lead Iodide Perovskites

Panzer

Meier

et al. 2017

Advanced Energy Materials

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“…28 Since the efficiency of the process decreases at lower temperatures (the transfer rate and the strength of the transfer component decrease with lowering of the temperature, compare Fig. 28 Since the efficiency of the process decreases at lower temperatures (the transfer rate and the strength of the transfer component decrease with lowering of the temperature, compare Fig.…”

Section: Resultsmentioning

confidence: 99%

A dual-phase architecture for efficient amplified spontaneous emission in lead iodide perovskites

et al. 2016

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Multi-particle Auger interactions are one of the major intrinsic limiting factors for lasing applications of lead halide perovskites. In this communication, we report a possible way to tackle this problem by investigating the transfer of the photo-excited population to radiative defect inclusions using transient absorption (TA) spectroscopy. We demonstrate a reduction of the threshold of amplified spontaneous emission (ASE) in the presence of an efficient transfer. 20133 Milano, Italy † Electronic supplementary information (ESI) available. See

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“…explained in terms of the more efficient higher-order processes of recombination at larger charge carriers densities.16 Figures S7-S10show that the TA and THz decays at the fluence of the absorbed photons of 0.72×10 13 ph/cm 2 are the same, which demonstrates that the observed mobility is due to a drop in the excited charge carriers concentration.16,44 In contrast to the TA decays upon excitation with the fluence of 9.4×10 13 ph/cm 2 , the THz ones do not show the presence of the 6 ps component attributed previously to the decay of excitons population. 16Page 15 of 39 Physical Chemistry Chemical PhysicsPhysical Chemistry Chemical Physics Accepted ManuscriptThus the time-resolved TA data along with the previous reports on the MAPbI 3 , present an evidence for exciton population at high fluences of the absorbed photons 36,45,52. 16Page 15 of 39 Physical Chemistry Chemical PhysicsPhysical Chemistry Chemical Physics Accepted ManuscriptThus the time-resolved TA data along with the previous reports on the MAPbI 3 , present an evidence for exciton population at high fluences of the absorbed photons 36,45,52.…”

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confidence: 87%

“…The increase in the fluence clearly affects the TA kinetic traces resulting in the appearance of new decaying components and in shortening of the existing ones. 21,31,45 It was reported that the change of methylammonium to formamidinium results in a change in the perovskite band structure giving rise to unbalanced electron and hole mobilities. For all the excitation wavelengths, we can distinguish three processes Figure S5 shows that the ∆OD -2 upon excitation at 400 nm using absorbed pump fluence of 6.9×10 13 ph/cm 2 is linear between 40 -900 ps.…”

Section: Femtosecond Dynamics At 775 Nm Observation Wavelengthmentioning

confidence: 99%

How photon pump fluence changes the charge carrier relaxation mechanism in an organic–inorganic hybrid lead triiodide perovskite

Piątkowski

Cohen

Kazim

et al. 2016

Phys. Chem. Chem. Phys.

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This study explores the excitation wavelength and fluence dependence of processes occurring in formamidinium lead triiodide (FAPbI) film using time-resolved transient absorption and terahertz spectroscopies. The results indicate that second-order processes are responsible for charge carrier recombination at low fluences of the absorbed photons (below 8.4 × 10 ph per cm). An increase in fluence leads to the appearance and successive reduction of the time component assigned to the Auger recombination of free charge carriers (240-120 ps). Simultaneously, the bimolecular recombination time decreases from ∼1400 to ∼700 ps. Further increasing the pump fluence produces an exciton population that recombines in 6 ps. The comparison of two characteristic bleaching bands located at 480 and 775 nm provides evidence for the validity of the two valence bands model. Excitation with higher fluences results in a marked difference in the probed dynamics at these bands, reflecting the action of two excited states at the conduction band. Our results demonstrate that a single model cannot be applied in characterizing the perovskite absorber transitions at all pump fluences. These findings are relevant in understanding their operating mechanism under specific experimental conditions, which should differ for perovskite based solar cells, lasing media or photon detectors.

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Exciton and Free Charge Dynamics of Methylammonium Lead Iodide Perovskites Are Different in the Tetragonal and Orthorhombic Phases

Cited by 67 publications

References 33 publications

Impact of Structural Dynamics on the Optical Properties of Methylammonium Lead Iodide Perovskites

Impact of Structural Dynamics on the Optical Properties of Methylammonium Lead Iodide Perovskites

A dual-phase architecture for efficient amplified spontaneous emission in lead iodide perovskites

How photon pump fluence changes the charge carrier relaxation mechanism in an organic–inorganic hybrid lead triiodide perovskite

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