Ultrafast photomodulation spectroscopy of π-conjugated polymers, nanotubes and organometal trihalide perovskites: A comparison

Sheng, C.-X.; Zhai, Yaxin; Huynh, Uyen; Zhang, Chuang; Vardeny, Z. Valy

doi:10.1016/j.synthmet.2015.09.013

Cited by 4 publications

(6 citation statements)

References 71 publications

(78 reference statements)

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“…In addition, the weak PA 2 band at ≈1 eV may be readily explained as the optical transition from the exciton level at ≈2.4 eV into higher-lying bands at ≈3.3 eV, which can be seen in the absorption spectrum (fig. S2), similar to the transient PM spectra of excitons in nanotubes and in CH 3 NH 3 PbI 3 ( 31 ).…”

Section: Resultssupporting

confidence: 63%

Giant Rashba splitting in 2D organic-inorganic halide perovskites measured by transient spectroscopies

et al. 2017

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Section: Resultssupporting

confidence: 63%

Giant Rashba splitting in 2D organic-inorganic halide perovskites measured by transient spectroscopies

et al. 2017

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“…As for the high-energy PIA, it was first attributed to the photo-induced change of the refractive index, while later studies disproved this argument using white light pulse interferometry to track the change in refractive index and by comparing the TA of films with NCs to quantify reflectivity contribution . Other explanations include the BGR effect, FCS effect and the destruction of the sample symmetry due to a photo-induced spatially inhomogeneous static strain . The existing inconsistencies indicate the necessity of extensive studies on the physical origin of the above-bandgap PIA.…”

Section: Results and Discussionmentioning

confidence: 99%

New Insights into Hot-Charge Relaxation in Lead Halide Perovskite: Dynamical Bandgap Change, Hot-Biexciton Effect, and Photo-Bleaching Shift

et al. 2022

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Harnessing hot-charge relaxation in lead halide perovskites (LHPs) is the key to developing next-generation high-performance concentrator solar cells that break the Shockley–Queisser limit. Though the physical origins of the slow hot-carrier cooling and their interplays have been unveiled, consensus is still lacking concerning the mechanisms of many-body interactions during hot-charge relaxation. Here, we propose a unified theory to explain the spectral and temporal evolution of the band edge in LHPs at the early time-scale following femtosecond laser excitation. We demonstrate that at early times, the hot-biexciton effect imposes a transient bandgap shrinkage decaying rapidly with exciton dissociation. Subsequently, bandgap renormalization (BGR) effect dominates the bandgap change, with a partial compensation by the free-carrier Stark (FCS) effect. Additionally, we confirmed that the shift in the photo-bleaching (PB) peak in the transient absorption (TA) spectra is modulated by carrier temperature rather than the bandgap change, which has negligible influence on the bleaching position, contrary to previous studies. Importantly, this work demonstrates the significant role played by the hot-biexciton interaction to the exciton generation-dissociation and carrier relaxation dynamics in perovskite solar cell materials at early times. Our insights resolve the existing contradictions on the nature of early-time photo-induced absorption and PB shift via reliable quantifications. By unraveling the role of hot-charge cooling and the intricate many-body interactions among the hot-biexciton interplay, BGR and FCS effects, our study contributes to a deeper comprehension of the fundamental photo-physics in LHPs.

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“…Vardeny et al give a plausible explanation for the photomodulation of the band edge on the blue side. 18 They proposed that the photoinduced excitations induce a static strain which is spatially inhomogeneous. This, in turn, breaks the symmetry of the sample, much like how an applied electric field does.…”

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“…Unlike the below-gap PIA, there is much controversy about the assignment of the above-gap PIA feature in the TA spectra of perovskite. First, because the PIA is broad and structureless, assignment to free carrier absorption is frequently encountered in the literature. ,, However, as argued by Vardeny and co-workers, , free carriers absorb photons in the mid-IR region while the above-gap PIA is in the visible region. Second, because the refractive index of perovskite is so high, Price and co-workers assigned the above-gap PIA of MAPbI 3 (methylammonium lead triiodide perovskites) to the photoinduced change of the refractive index instead of a change in absorbance .…”

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Observation of Charge Generation via Photoinduced Stark Effect in Mixed-Cation Lead Bromide Perovskite Thin Films

Tran

Elkins

McMeekin

et al. 2020

J. Phys. Chem. Lett.

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Extensive transient absorption studies on hybrid organic–inorganic lead halide perovskites have elucidated many optical properties important for their device performance. Despite the enormous progress, the derivative shaped photoinduced absorption feature in transient spectra that is above the bandgap has many explanations, including the photoinduced Stark effect, where the bandgap is blue shifted due to a local electric field generated by charges. In this work, we employ broad band transient absorption and two-dimensional electronic spectroscopy (2DES) to examine the early transient events after photoexcitation of [CH(NH2)2]0.83Cs0.17PbBr3 (FA0.83Cs0.17PbBr3). 2DES resolves a photomodulation feature at the excitation energy of the exciton, suggesting the presence of a dipole field created by a polaron pair shifting the exciton transition to higher energies. As this polaron pair dissociates over 200 fs, the exciton transition shifts to higher energies over the same time scale, evidenced by the 2DES diagonal energy spectra. Given that the observations are well explained in terms of the Stark effect, our work provides extra grounds to support the Stark effect assignment of the above-gap photoinduced absorption. Furthermore, our study reports on the time scale of charge generation, contributing to the fundamental understanding of mixed-cation lead bromide perovskite photophysics.

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Ultrafast photomodulation spectroscopy of π-conjugated polymers, nanotubes and organometal trihalide perovskites: A comparison

Abstract: We compare the ultrafast dynamics of the primary photoexcitations in various -conjugated organic semiconductors, semiconducting single-walled carbon nanotubes (S-NTs) and organometaltrihalide perovskites including CH 3 NH 3 PbI 3

Cited by 4 publications

References 71 publications

Giant Rashba splitting in 2D organic-inorganic halide perovskites measured by transient spectroscopies

Giant Rashba splitting in 2D organic-inorganic halide perovskites measured by transient spectroscopies

New Insights into Hot-Charge Relaxation in Lead Halide Perovskite: Dynamical Bandgap Change, Hot-Biexciton Effect, and Photo-Bleaching Shift

Observation of Charge Generation via Photoinduced Stark Effect in Mixed-Cation Lead Bromide Perovskite Thin Films

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