Controlled Growth of CH3NH3PbI3 Using a Dynamically Dispensed Spin‐Coating Method: Improving Efficiency with a Reproducible PbI2 Blocking Layer

Ma, Yunlong; Vashishtha, Parth; Chen, Kai; Peach, Elijah L.; Ohayon, David; Hodgkiss, Justin M.; Halpert, Jonathan E.

doi:10.1002/cssc.201700449

Cited by 21 publications

(15 citation statements)

References 41 publications

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“…This result reveals that the excess of PbI 2 in the film and/or the interfacial intermediate phase layer modifies substantially the mechanism of nucleation, yielding in this case to isotropic MAPbI 3 .H 2 O particles. [ 20g,22 ] Figure 4b compares the evolution of the most intense XRD peaks corresponding to MAPbI 3 , MAPbI 3 .H 2 O, and PbI 2 as a function of aging time. Under the same exposure conditions, MAPbI 3 with 9 mol% excess of PbI 2 exhibits subtle variation in the degradation pathway.…”

Section: Resultsmentioning

confidence: 99%

Molecular‐Level Insight into Correlation between Surface Defects and Stability of Methylammonium Lead Halide Perovskite Under Controlled Humidity

et al. 2020

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Perovskite‐based photovoltaics (PVs) have garnered tremendous interest, enabling power conversion efficiencies exceeding 25%. Although much of this success is credited to the exploration of new compositions, defects passivation and process optimization, environmental stability remains an important bottleneck to be solved. The underlying mechanisms of thermal and humidity‐induced degradation are still far from a clear understanding, which poses a severe limitation to overcome the stability issues. Herein, in situ X‐ray diffraction (XRD), in operando liquid‐cell transmission electron microscopy (TEM) and ex situ solid‐state (ss)NMR spectroscopy are combined with time‐resolved spectroscopies to reveal new insights about the degradation mechanisms of methylammonium lead halide (MAPbI3) under 85% relative humidity (RH) at different length scales. Liquid‐cell TEM enables the live visualizations from meso‐to‐nanoscale transformation between the perovskite particles and water molecules, which are corroborated by the changes in local structures at sub‐nanometer distances by ssNMR and longer range by XRD. This work clarifies the role of surface defects and the significance of their passivation to prevent hydration and decomposition reactions.

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Section: Resultsmentioning

confidence: 99%

Molecular‐Level Insight into Correlation between Surface Defects and Stability of Methylammonium Lead Halide Perovskite Under Controlled Humidity

et al. 2020

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“…25,26 From a more fundamental perspective, it has been demonstrated that recombination between charge carriers in the absorber and transport layers have been suppressed due to a thin interfacial layer of PbI 2 . [27][28][29] In regard to charge carriers that form in the perovskite absorber, both a reduction of non-radiative recombination, and accelerated recombination with an excess of PbI 2 has been reported. [30][31][32] These reports do not necessarily contradict one another but may rather reflect a dependence on where, and how PbI 2 has been introduced in the perovskite.…”

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confidence: 99%

Impact of Excess Lead Iodide on the Recombination Kinetics in Metal Halide Perovskites

et al. 2019

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Fundmental comprehension of light-induced processes of perovskites are still scarce. One active debate surrounds the influence of excess lead iodide (PbI 2) on device performance, as well as optoelectronic properties, where both beneficial and detrimental traits have been reported. Here, we study its impact on the charge-carrier recombination kinetics by simultaneously acquiring photoluminescence quantum yield and time-resolved photoluminescence as a function of excitation wavelength (450 nm-780 nm). The presence of PbI 2 in the perovskite film is identified via a unique spectroscopic signature in the PLQY spectrum. Probing the recombination in the presence and absence of this signature, we detect a radiative bimolecular recombination mechanism induced by PbI 2. Spatially resolving the photoluminescence, we determine that this radiative process occurs in a small volume at the PbI 2 /perovskite interface, which is only active when charge carriers are generated in PbI 2 , and therefore provide deeper insight into how excess PbI 2 may improve the properties of perovskite based devices.

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“…That means the optical properties can be tuned by changing the ratio between halides in the perovskite structure. All of these properties are very useful for optoelectronic applications, such as solar cells, LEDs, photodetectors, and laser applications [14][15][16].…”

Section: Introductionmentioning

confidence: 99%

“…relatively high charge mobility and conductivity, and low temperature particle fusion from 1D and 2D structures [16,35,36,38,137,236] NCs [24,[239][240][241][242]. MAPI is one of the well characterised 3D structured perovskite used for constructing highly efficient photodetector, solar cells and LEDs [15,[243][244][245][246][247]. Therefore, finding novel perovskite and related nanomaterials with useful relevant properties is a major area of research in this field and many researchers have been working to replace A and B groups in the ABX 3 perovskite structure with feasible atom such as Bi, In, Ag, Sn, and Cu [22][23][24][25].…”

Section: Introductionmentioning

confidence: 99%

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Nanostructured Inorganic Metal Halide Perovskites for Optoelectronic Applications

Vashishtha¹

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Semiconductor quantumdots have proven to be promising materials for optoelectronic devices, such as light emitting devices (LEDs) and solar cells, due to their thin linewidth of emission, high photoluminescence quantum yield and high absorption coefficient. Over the last decade, perovskite crystals have gained significant attention due to their extraordinary optoelectronic properties. Therefore, perovskite nanocrystals combine the advantage of both crystalline perovskite and quantum dots. Here, we synthesised high quantum yield (50 - 80 %) monodispersed CsPbX₃ (X= Cl, Br, I) quantum dots, with tuneable emission spectra over the entire visible region, by a colloidal synthesis method. We have then successfully processed them to produce thin films as the emitting layer in an organic LED-type device architecture. Most importantly, we demonstrated field induced halide separation in mixed halide CsPb(Br/I)₃ NCs which is the reason color instability in these LEDs. Perovskite nanocrystal LEDs were found to have low external quantum efficiency (EQE) due to their bulky ligands. As a result, Ruddlesden-Popper (RP) phase layered perovskite was investigated to increase the EQE over perovskite QD LEDs. As a result, we constructed RP perovskite phase CsPbX₃ LEDs with emission through the entire visible spectrum (460-700 nm). Colour tuning was achieved by taking advantage of both quantum confinement effect and halide mixing. The EQE of these LEDs outperformed the literature values in the blue and blue-green spectral regions, with relatively long life time. We also invented a novel perovskite nanocrystals made from thalliumlead halide by replacing caesium with thallium. These materials are potential candidates for various optoelectronic applications. Size-, shape-, and composition- tuning in these nanocrystals were performed by varying the reaction conditions andmixing the halide composition. A weak confinementwas observed in these NCs. Additionally, we have shown the application of TlPbI₃ nanowires as photoconductors. Collectively, this thesis includes the synthesis of various types of inorganic metal halide perovskite nanostructures followed by their implementation into working optoelectronic devices, specifically LEDs.

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Controlled Growth of CH₃NH₃PbI₃ Using a Dynamically Dispensed Spin‐Coating Method: Improving Efficiency with a Reproducible PbI₂ Blocking Layer

Cited by 21 publications

References 41 publications

Molecular‐Level Insight into Correlation between Surface Defects and Stability of Methylammonium Lead Halide Perovskite Under Controlled Humidity

Molecular‐Level Insight into Correlation between Surface Defects and Stability of Methylammonium Lead Halide Perovskite Under Controlled Humidity

Impact of Excess Lead Iodide on the Recombination Kinetics in Metal Halide Perovskites

Nanostructured Inorganic Metal Halide Perovskites for Optoelectronic Applications

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