Photo-induced halide redistribution in organic–inorganic perovskite films

deQuilettes, Dane W.; Zhang, Wei; Burlakov, V. M.; Graham, Daniel J.; Leijtens, Tomas; Osherov, Anna; Bulović, Vladimir; Snaith, Henry J.; Ginger, David S.; Stranks, Samuel D.

doi:10.1038/ncomms11683

Cited by 823 publications

(964 citation statements)

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“…Additionally, the PL intensity was found to be enhanced during the continuous light soaking experiment but significantly diminished when the irradiation was turned off; this was ascribed to an order of magnitude reduction in trap state density. [150] This finding is further supported by depth profiling via time-of-flight secondary ion mass spectrometry, where the locations with lowest illumination intensity exhibited high levels of I − ions. Their work demonstrates the intricate relation between trap density and migration of iodine species.…”

Section: Ion Migrationsupporting

confidence: 59%

Low‐Dimensional Perovskites: From Synthesis to Stability in Perovskite Solar Cells

Yusoff

Nazeeruddin

2017

Advanced Energy Materials

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ruthenium molecular dye, wide absorption range, direct and tunable bandgaps, superior charge carrier mobility, and long carrier diffusion length. [6,[43][44][45] Although it has been synthesized for over 100 years, Mitzi et al. were the first to investigate the electrical properties of tin-based perovskite in 1994, [46] which was later used in numerous devices, including field effect transistors (FETs) and LEDs. [47][48][49] The attention toward metal halide perovskites sparked yet again in 2009, [42] and they were later named one of the most promising emerging technologies in 2016. In brief, metal halide perovskites can be divided into two types based on their crystal structure motif: (i) 3D-structured perovskite (AMX 3 ) and (ii) 2D-structured perovskite (A 2 MX 4 ). The structure of the perovskite could either be 2D or 3D, while the dimensions of the perovskite probably belong to 0D-3D. The term "perovskite" implies to the general class of materials derived from an elemental composition of AMX 3 and demonstrates the crystal structure of perovskite crystal CaTiO 3 , where the divalent metal M resides at the body center and surrounded by six X-anions located at the face centers in an octahedral cluster. The MX 6 in the octahedral cluster may form an extended 3D structure by all-corner-connected type with A-cation sitting at the center. It could also form a 2D perovskite when the 3D perovskite network is cut into one-layer-thick slices along the 〈100〉 direction and separates them apart. In principle, 2D perovskite is the easiest to synthesize because of its natural layered structure, which is held together by weak van der Waals forces. Dou et al. reported the large-scale synthesis of the monolayer (C 4 H 9 NH 3 ) 2 -PbBr 4 by a chemical method. [50] Along the same lines, several groups have prepared and characterized nanomaterials composed of various forms of perovskites. [51][52][53] Also, our group has recently successfully prepared a low-dimensional mixed 2D/3D perovskite using the protonated salt of amino valeric acid iodide (AVAI) as an organic precursor mixed with PbI 2 , in which a yellowish film was containing needle-like crystallite formed. [54] In this topical review, we present the latest advances in the synthesis of low-dimensional perovskites and the growth mechanism to develop a strategy to achieve best performing devices. Later, we focus the instability and a cost-effective solution to circumvent this problem, which is vital for the eventual deployment of perovskite solar cells to consumers market. We present an analysis of the origins for instability in perovskite solar cells, and present a summary of the main achievements and possible future developments of these low-dimensional perovskite. [2,55] Perovskite solar cells have been heralded as one of the most promising emerging technologies in 2016 because of the very high power conversion efficiency of 22% and the low cost of generating electricity compared to even fossil fuels. These are formed with various dimensionalities and can be fully mani...

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Section: Ion Migrationsupporting

confidence: 59%

Low‐Dimensional Perovskites: From Synthesis to Stability in Perovskite Solar Cells

Yusoff

Nazeeruddin

2017

Advanced Energy Materials

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“…phase stable compositions) and is linked to a filling and stabilization of charge trap states by photo generated electrons; additionally, the long time constants associated with this process may indicate contributions from the slow motion of ions. 24,25 With higher Brconcentration (x = 0.6), the clear appearance of an additional higher wavelength emission peak is observed (Figure 2c and Supporting Information S4) and is attributed to formation of an Irich phase with lower bandgap. However, the threshold for photoinduced halide segregation occurs at significantly higher Br content for the case of FACsPbhalide perovskites.…”

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confidence: 95%

Cation-Dependent Light-Induced Halide Demixing in Hybrid Organic–Inorganic Perovskites

et al. 2018

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Mixed cation metal halide perovskites with increased power conversion efficiency, negligible hysteresis, and improved long term stability under illumination, moisture, and thermal stressing have emerged as promising compounds for photovoltaic and optoelectronic applications. Here, we shed light on photoinduced halide demixing using insitu photoluminescence spectroscopy and synchrotron Xray diffraction (XRD) to directly compare the evolution of composition and phase changes in CH(NH 2 ) 2 CsPbhalide (FACsPb) and CH 3 NH 3 Pbhalide (MAPb) perovskites upon illumination, thereby providing insights into why FACsPbhalides are less prone to halide demixing than MAPbperovskites. We find that halide demixing occurs in both materials.However, the formed Irich domains accumulate strain for the case of FACsPbperovskites but readily relax for the case of MAPbperovskites. The accumulated strain energy is expected to act as a stabilizing force against halide demixing and may explain the higher Br composition threshold for demixing to occur in FACsPbhalides. In addition, we find that while halide demixing leads to a quenching of the high energy photoluminescence emission from MA 2 perovskites, the emission is enhanced for the case of FaCsperovskites. This behavior points to a reduction of nonradiative recombination centers in FACsperovskites arising from the demixing process. FACsPbhalide perovskites exhibit excellent intrinsic material properties, with photoluminescence quantum yields that are comparable to MAperovskites. Since improved stability is achieved without sacrificing electronic properties, these compositions are better candidates for photovoltaic applications, especially as wide bandgap absorbers in tandem cells. , and high photoluminescence quantum yields 2,4 . Their general crystal structure is described by ABX 3 , typically comprising a monovalent organic cation A (e.g. Despite the importance of overcoming halide demixing for achieving stable perovskitebased photovoltaic devices, there remains uncertainty about the underlying mechanism(s) and most studies have focused on MAperovskites. Currently, strain or carrierinduced lattice distortion, 6 compositional inhomogeneity, 7 defectmediated halide migration, 6,8,9 and crystal domain size 10 are actively considered as contributing to halide segregation. In particular, Bischak et al. propose that halide demixing is a consequence of localized strain generated from the interaction of charge carriers with the lattice (polaron formation). 6In this respect, they find that the combination of 4 mobile halides, long charge carrier lifetimes, and significant electronphonon coupling are prerequisites for halide demixing. 6 In a different study, Barker et al. suggest that defectassisted halide ion migration away from the illuminated surface, with a slower hopping rate of iodide and a potential dependence on charge carrier generation gradients, results in formation of Irich regions at the surface. In this explanation, they argue that halide segregation in a single cr...

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“…Such slow dynamics of the PL of bulk MAPbI 3 has been previously observed in the past, [29,30] and has been proposed to originate at trap-filling caused by the photoinduced migration of ions within the perovskite lattice under illumination. [31] Within this picture it is reasonable to assume that the time needed for ions to traverse the size of the nanocrystal should be orders of magnitude smaller than that for the bulk case. This observation suggests that, under similar excitation conditions, the PL of nanocrystals enters the so-called bimolecular regime, in which carrier decay rate is dominated by radiative recombination, [32] much faster than that of bulk crystals, which remains for longer in the monomolecular regime, in which nonradiative trap filling prevails.…”

Section: Doi: 101002/adom201601087mentioning

confidence: 99%

Strong Quantum Confinement and Fast Photoemission Activation in CH₃NH₃PbI₃ Perovskite Nanocrystals Grown within Periodically Mesostructured Films

Anaya

Rubino

Rojas

et al. 2017

Advanced Optical Materials

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CommuniCation(1 of 7) 1601087 synthesis of PbI 2 nanocrystals and their subsequent reaction with CH 3 NH 3 I 3 to produce the corresponding organic-inorganic lead halide quantum dots. [4] More recently, powders of porous silica exhibiting a 2D hexagonal mesopore structure have been used as templates to synthesize MAPbI 3 nanocrystals. [14,15] This approach proved to be suitable to attain bright and stable emission whose spectrum could be controlled by the average pore size of the matrix. However, most applications foreseen for hybrid perovskites require the use of thin films of high optical quality, as well as versatility regarding the composition of the scaffold employed. In order to achieve this goal, mesostructures with geometries other than the hexagonal one previously employed to host perovskite nanocrystals must be used, since the characteristic tubular channels tend to lie parallel to the substrate when the porous material is shaped as a film, becoming inaccessible from the top surface. This prevents their infiltration with perovskite precursors. Very recently, MAPbI 2 X (X = Cl, Br, I) compounds have been synthesized inside metal organic framework films, [16] but no control over the size and optical properties of MAPbI 3 was demonstrated.In this Communication, we demonstrate a synthetic route to obtain stabilized MAPbI 3 nanocrystals embedded in thin metal oxide films that display well-defined and adjustable quantum confinement effects over a wide range of 0.34 eV. Mesostructured TiO 2 and SiO 2 films displaying an ordered 3D pore network are prepared by evaporation induced self-assembly of a series of organic supramolecular templates in the presence of metal oxide precursors. The pores in the inorganic films obtained after thermal annealing are then used as nanoreactors to synthesize MAPbI 3 crystallites with narrow size distribution and average radius comprised between 1 and 4 nm, depending on the template of choice. Both the static and dynamic photoemission properties of the ensemble display features distinctive of the regime of strong quantum confinement. Photoemission maps demonstrate that the spectral and intensity properties of the luminescence extracted from the perovskite quantum dot loaded films are homogeneous over squared centimeters areas. In addition, the photoemission stationary state is reached 10 4 times faster than in a MAPbI 3 solid film. One of the most versatile strategies to tune the optical properties of a semiconductor consists in reducing its size until it becomes of the order of the exciton Bohr radius and quantum confinement effects arise. [1] Different methods have been developed to try to controllably diminish the size of methyl ammonium lead halide (MAPbX 3 , X = Cl, Pb, I) crystals, [2][3][4][5][6][7] motivated by the interest these perovskites generate in the field of optoelectronics. [8][9][10][11][12] Efforts in obtaining dispersions of hybrid organic-inorganic perovskite nanocrystals for optoelectronic applications have mainly focused on MAPbBr 3 and MAPbBr x I 3-x , a...

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Photo-induced halide redistribution in organic–inorganic perovskite films

Cited by 823 publications

References 51 publications

Low‐Dimensional Perovskites: From Synthesis to Stability in Perovskite Solar Cells

Low‐Dimensional Perovskites: From Synthesis to Stability in Perovskite Solar Cells

Cation-Dependent Light-Induced Halide Demixing in Hybrid Organic–Inorganic Perovskites

Strong Quantum Confinement and Fast Photoemission Activation in CH₃NH₃PbI₃ Perovskite Nanocrystals Grown within Periodically Mesostructured Films

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Photo-induced halide redistribution in organic–inorganic perovskite films

Cited by 823 publications

References 51 publications

Low‐Dimensional Perovskites: From Synthesis to Stability in Perovskite Solar Cells

Low‐Dimensional Perovskites: From Synthesis to Stability in Perovskite Solar Cells

Cation-Dependent Light-Induced Halide Demixing in Hybrid Organic–Inorganic Perovskites

Strong Quantum Confinement and Fast Photoemission Activation in CH3NH3PbI3 Perovskite Nanocrystals Grown within Periodically Mesostructured Films

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Strong Quantum Confinement and Fast Photoemission Activation in CH₃NH₃PbI₃ Perovskite Nanocrystals Grown within Periodically Mesostructured Films