Synthetic control over orientational degeneracy of spacer cations enhances solar cell efficiency in two-dimensional perovskites

Hu, Jun; Oswald, Iain W. H.; Stuard, Samuel J.; Nahid, Masrur Morshed; Zhou, Ninghao; Williams, Olivia F.; Guo, Zhenkun; Yan, Liang; Hu, Huamin; Chen, Zheng; Xiao, Xun; Lin, Yun; Yang, Zhibin; Huang, Jinsong; Moran, Andrew M.; Ade, Harald; Neilson, James R.; You, Wei

doi:10.1038/s41467-019-08980-x

Cited by 245 publications

(305 citation statements)

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“…The theoretical calculation also predicted that a fluorine‐substituted organic spacer may distort the crystal structure of perovskite . Very recently, during our paper submission process, several latest publications also experimentally demonstrate that the fluorination of organic spacer cations can impact on the perovskite crystal structure and photovoltaic performance …”

Section: Summary Of Photovoltaic Parameters For the Devices With (Peamentioning

confidence: 75%

Fluorinated Low‐Dimensional Ruddlesden–Popper Perovskite Solar Cells with over 17% Power Conversion Efficiency and Improved Stability

et al. 2019

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The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/adma.201901673.Low-dimensional Ruddlesden-Popper perovskites (RPPs) exhibit excellent stability in comparison with 3D perovskites; however, the relatively low power conversion efficiency (PCE) limits their future application. In this work, a new fluorine-substituted phenylethlammonium (PEA) cation is developed as a spacer to fabricate quasi-2D (4FPEA) 2 (MA) 4 Pb 5 I 16 (n = 5) perovskite solar cells. The champion device exhibits a remarkable PCE of 17.3% with a J sc of 19.00 mA cm −2 , a V oc of 1.16 V, and a fill factor (FF) of 79%, which are among the best results for low-dimensional RPP solar cells (n ≤ 5). The enhanced device performance can be attributed as follows: first, the strong dipole field induced by the 4-fluoro-phenethylammonium (4FPEA) organic spacer facilitates charge dissociation. Second, fluorinated RPP crystals preferentially grow along the vertical direction, and form a phase distribution with the increasing n number from bottom to the top surface, resulting in efficient charge transport. Third, 4FPEA-based RPP films exhibit higher film crystallinity, enlarged grain size, and reduced trap-state density. Lastly, the unsealed fluorinated RPP devices demonstrate superior humidity and thermal stability. Therefore, the fluorination of the long-chain organic cations provides a feasible approach for simultaneously improving the efficiency and stability of low-dimensional RPP solar cells. Perovskite Solar CellsOrganic-inorganic hybrid perovskites have attracted tremendous attention due to their high absorption coefficients, [1] high charge carrier mobility, [2] high defect tolerance, [3] and long diffusion lengths. [4] Although the power conversion efficiency (PCE) of perovskite solar cells (PSCs) has reached 23.32% in the past few years, the intrinsic material instability of 3D perovskites still remain unresolved, which hinder the future commercialization of perovskite solar cells. [5] Compared

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Section: Summary Of Photovoltaic Parameters For the Devices With (Peamentioning

confidence: 75%

Fluorinated Low‐Dimensional Ruddlesden–Popper Perovskite Solar Cells with over 17% Power Conversion Efficiency and Improved Stability

et al. 2019

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“…Previous work showed that thin films of stoichiometric n = 4 layered perovskites contain mixed phases of n = 1, 2, 3 layered perovskite as well as the corresponding 3D phase, such as (FA)PbI 3 . [ 38 ] Because of the large spacing (created by organic spacer molecules like PEA) between the strong scattering lead‐iodide layers in layered perovskites, only layered perovskite phases (and not the bulk phase) can generate scattering momentum transfers less than 10 nm −1 (since there is an inverse relationship between real spacing and reciprocal spacing). [ 39 ] In the present DMSO pattern, three scattering signatures at less than 10 nm −1 are noticeable.…”

Section: Figurementioning

confidence: 99%

Efficient Energy Funneling in Quasi‐2D Perovskites: From Light Emission to Lasing

et al. 2020

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high photoluminescence quantum yield (PLQY), wide wavelength tunability, and high color purity, [4][5][6] they have been attractive for light-emitting diode (LED) applications. Since the first demonstration of perovskite LEDs in 2014, [7] the device external quantum efficiency (EQE) has risen rapidly from 0.1% [7] to ≈20%, [2,4,8] and the efficiency enhancements are mainly attributed to passivation and compositional engineering, [2,8] improved charge balance by optimization of device structure, [9] and efficient light extraction. [4] More recently, these materials are considered as optical gain medium for lasers. In 2014, the first amplified spontaneous emission (ASE) was observed from CH 3 NH 3 PbI 3 thin films with a threshold of 12 µJ cm −2 and a gain of 250 cm −1 , which is ascribed to the large absorption coefficient, low bulk defect density, and slow Auger recombination rate. [10] These ASE threshold and gain values are comparable to the state of art gain media such as colloidal quantum dots [11] and organic thin films. [12] Since then, optically pumped lasers have been demonstrated based on various microcavity structures such as Fabry-Pérot cavities, [13,14] distributed feedback (DFB) gratings, [3,15] and whispering gallery cavities. [16] The flexibility of fabricating hybrid perovskite lasers using solution-processed methods enables large-scale production and is attractive for the realization of on-chip integration of photonic circuits. [17] Quasi-2D perovskites, which are also known as Ruddlesden-Popper (RP) perovskites, are mixed phases of 2D and 3D nanocrystals. In the mixture, 2D domains exhibit quantumwell-like electronic properties with strong exciton binding energy due to the reduced dimensionality. [18] Typically, the 2D perovskite (A') 2 A n−1 B n X 3n+1 domains consist of multilayers of BX 6 octahedra separated by intercalating ammonium cations A', which is too large to fit into the crystal structure and hinder the growth of 3D ABX 3 crystals (A = methylammonium (MA + ), formamidinium (FA + ), or Cs + , B = Pb 2+ , and X = I − , Br − , Cl − ). As a result, the number of layers determine the bandgap of 2D quantum-well-like domains. [19] Different from 3D perovskites, thin films of qausi-2D perovskites typically contain a mixture of domains with different layers. Within such inhomogenous Quasi-2D Ruddlesden-Popper halide perovskites with a large exciton binding energy, self-assembled quantum wells, and high quantum yield draw attention for optoelectronic device applications. Thin films of these quasi-2D perovskites consist of a mixture of domains having different dimensionality, allowing energy funneling from lower-dimensional nanosheets (high-bandgap domains) to 3D nanocrystals (low-bandgap domains). High-quality quasi-2D perovskite (PEA) 2 (FA) 3 Pb 4 Br 13 films are fabricated by solution engineering. Grazing-incidence wide-angle X-ray scattering measurements are conducted to study the crystal orientation, and transient absorption spectroscopy measurements are conducted to study the charge-carr...

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“…As a result, the optical and electronic properties of the materials can be tuned not only by metal cation and halide anion but also organic molecules with different sizes and functional groups, providing almost unlimited compositional and structural versatility. Given the vast design space for both organic and inorganic components, more “exotic” functions have also been envisioned with 2D hybrid perovskites, including singlet fission, room‐temperature phosphorescence and third harmonic generation …”

Section: Figurementioning

confidence: 99%

Reversible Thermochromism and Strong Ferromagnetism in Two‐Dimensional Hybrid Perovskites

Sun

Liu

et al. 2019

Angewandte Chemie

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Two‐dimensional (2D) hybrid perovskites have shown many attractive properties associated with their soft lattices and multiple quantum well structure. Herein, we report the synthesis and characterization of two new multifunctional 2D hybrid perovskites, (PED)CuCl4 and (BED)2CuCl6, which show reversible thermochromic behavior, dramatic temperature‐dependent conductivity change, and strong ferromagnetism. Upon temperature change, the (PED)CuCl4 and (BED)2CuCl6 crystals exhibit a reversible color change between yellow and red‐brown. The associated structural changes were monitored by in situ temperature‐dependent powder X‐ray diffraction (PXRD). The (BED)2CuCl6 exhibits superior thermal stability, with a thermochromic working temperature up to 443 K. The conductivity of (BED)2CuCl6 changes over six orders of magnitude upon temperature change. The 2D perovskites exhibit ferromagnetic properties with Curie temperatures around 13 K.

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Synthetic control over orientational degeneracy of spacer cations enhances solar cell efficiency in two-dimensional perovskites

Cited by 245 publications

References 72 publications

Fluorinated Low‐Dimensional Ruddlesden–Popper Perovskite Solar Cells with over 17% Power Conversion Efficiency and Improved Stability

Fluorinated Low‐Dimensional Ruddlesden–Popper Perovskite Solar Cells with over 17% Power Conversion Efficiency and Improved Stability

Efficient Energy Funneling in Quasi‐2D Perovskites: From Light Emission to Lasing

Reversible Thermochromism and Strong Ferromagnetism in Two‐Dimensional Hybrid Perovskites

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