The Raman Spectrum of the CH3NH3PbI3 Hybrid Perovskite: Interplay of Theory and Experiment

Quarti, Claudio; Grancini, Giulia; Mosconi, Edoardo; Bruno, P.; Ball, James M.; Lee, Michael M.; Snaith, Henry J.; Petrozza, Annamaria; Angelis, Filippo De

doi:10.1021/jz402589q

Cited by 599 publications

(825 citation statements)

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“…The coupling constant is α p = me 4 /2 2 2 * E LO , where E LO is the energy of the longitudinal optical phonon, and 1/ * = 1/ ∞ − 1/ 0 . Using the values E LO = 38.4 meV [47], ∞ / 0 = 0.235 [33], and the HSE + SO effective masses, we obtain 0.21 and 0.27 for the electron and hole polaron masses, respectively. The polaron energy shifts, E p = −α p E LO , are −49 and −44 meV for the hole and the electron, respectively.…”

Section: Discussionmentioning

confidence: 94%

Self-consistent relativistic band structure of theCH3NH3PbI3perovskite

et al. 2014

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The electronic structure and properties of the orthorhombic phase of the CH 3 NH 3 PbI 3 perovskite are computed with density functional theory. The structure, optimized using a van der Waals functional, reproduces closely the unit cell volume. The experimental band gap is reproduced accurately by combining spin-orbit effects and a hybrid functional in which the fraction of exact exchange is tuned self-consistently to the optical dielectric constant. Including spin-orbit coupling strongly reduces the anisotropy of the effective mass tensor, predicting a low electron effective mass in all crystal directions. The computed binding energy of the unrelaxed exciton agrees with experimental data, and the values found imply a fast exciton dissociation at ambient temperature. Also polaron masses for the separated carriers are estimated. The values of all these parameters agree with recent indications that fast dynamics and large carrier diffusion lengths are key in the high photovoltaic efficiencies shown by these materials.

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Section: Discussionmentioning

confidence: 94%

Self-consistent relativistic band structure of theCH3NH3PbI3perovskite

et al. 2014

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“…X-ray diffraction (XRD) has shown a lower symmetry structure at room temperature [26] and Raman spectra confirm the intrinsic MA vibrational mode which gives rise to the intrinsic dipole inside [27]. In addition, electroabsorption spectroscopy, or Stark spectroscopy [28], provides the unambiguous evidence of a permanent dipole in the organolead halide perovskite [10,29].…”

Section: Ferroelectricitymentioning

confidence: 96%

Origins and mechanisms of hysteresis in organometal halide perovskites

Guerrero

Zhong

et al. 2017

J. Phys.: Condens. Matter

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Inorganic–organic halide organometal perovskites, such as CH3NH3PbI3 and CsPbI3, etc, have been an unprecedented rising star in the field of photovoltaics since 2009, owing to their exceptionally high power conversion efficiency and simple fabrication processability. Despite its relatively short history of development, intensive investigations have been concentrating on this material; these have ranged from crystal structure analysis and photophysical characterization to performance optimization and device integration, etc. Yet, when applied in photovoltaic devices, this material suffers from hysteresis, that is, the difference of the current–voltage (I–V) curve during sweeping in two directions (from short-circuit towards open-circuit and vice versa). This behavior may significantly impede its large-scale commercial application. This Review will focus on the recent theoretical and experimental efforts to reveal the origin and mechanism of hysteresis. The proposed origins include (1) ferroelectric polarization, (2) charge trapping/detrapping, and (3) ion migration. Among them, recent evidence consistently supports the idea that ion migration plays a key role for the hysteretic behavior in perovskite solar cells (PSCs). Hence, this Review will summarize the recent results on ion migration such as the migrating ion species, activation energy measurement, capacitive characterization, and internal electrical field modulation, etc. In addition, this Review will also present the devices with alleviation/elimination of hysteresis by incorporating either large-size grains or phenyl-C61-butyric acid methyl ester molecules. In a different application, the hysteretic property has been utilized in photovoltaic and memristive switching devices. In sum, by examining these three possible mechanisms, it is concluded that the origin of hysteresis in PSCs is associated with a combination of effects, but mainly limited by ion/defect migration. This strong interaction between ion motion and free charge carrier transport can be modulated by the prevalent crystalline structure, chemical passivation, and an external photo/electrical field.

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“…Raman vibrational analysis exist for clean PVK thin films [18][19][20] which may be a consequence of Raman conditions employed. Our Raman spectroscopy results on the black areas of the films at ambient conditions (excitation wavelength (ex) 532nm) showed bands at 97, 112, 171 and 220 cm -1 attributed to Pb-I bonds and organic cation motions and is consistent with a prior study (Fig.…”

Section: Various Sometimes Contradictory Interpretations Of Theoretimentioning

confidence: 99%