Influence of Solvent Swelling on Ultrafast Structural Dynamics in Polydimethylsiloxane Thin Films by Two-Dimensional IR Spectroscopy

Olson, Courtney M.; Massari, Aaron M.

doi:10.1021/acs.jpca.7b12128

Cited by 3 publications

(1 citation statement)

References 77 publications

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“…Being motivated by the need to investigate polaron formation in lead-halide perovskites as the putative origin of energetic barriers that slow down charge recombination, we examined the structural dynamics of the perovskite lattice following photoexcitation using temperature-dependent time-resolved infrared (TRIR) spectroscopy. TRIR spectroscopy provides the opportunity to examine phonon and electronic dynamics in materials ranging from molecular solids − and glasses − to liquids − and proteins. − In systems where vibrational lineshapes are dynamically broadened, structural dynamics can be examined through temperature-dependent measurements of the vibrational line widths. For example, structural dynamics in a supercooled chalcogenide glass were examined through temperature-dependent measurements of the linewidths of the phonon modes .…”

Section: Introductionmentioning

confidence: 99%

Vibrational Probe of the Structural Origins of Slow Recombination in Halide Perovskites

et al. 2019

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We use time-resolved vibrational spectroscopy to probe the structural origins of the remarkably long charge recombination lifetimes of halide perovskites. The N−H bend vibrational mode of CH 3 NH 3 + organic cations is coupled to the inorganic perovskite lattice and provides a means to examine the structural fluctuations of the crystalline lattice of CH 3 NH 3 PbI 3 films. In the excited electronic state, the photogeneration of charge carriers causes the N−H bend vibrational dephasing dynamics to become very sensitive to temperature, revealing large changes in the amplitude of the structural motions of the lattice within a narrow 150−300 K temperature range of the tetragonal phase. The larger amplitude fluctuations of the lattice at elevated temperatures inhibit delocalization of photogenerated charges, causing them to self-trap into large polarons with delocalization lengths that decrease more than 30% as the temperature increases from 150 to 300 K. This self-trapping into large polarons introduces energetic barriers that decrease the capture cross section for electron/hole recombination by an order of magnitude at elevated temperatures. These findings indicate that the slow charge recombination kinetics of halide perovskites underpinning many of their remarkable properties are traced to the formation of energetic barriers that hinder wavefunction overlap of oppositely charged carriers in large polaron states. The findings also suggest that substitution of differently sized ions in halide perovskites can be used to tune the balance of charge transport versus charge recombination for photovoltaic or light-emitting applications because ions influence the structural flexibility and therefore the self-trapping of charge carriers into large polarons.

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Section: Introductionmentioning

confidence: 99%

Vibrational Probe of the Structural Origins of Slow Recombination in Halide Perovskites

et al. 2019

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Two Dimensional Infrared Spectroscopy: A Structure Sensitive Technique with Ultrafast Time Resolution

Ghosh

Deshmukh

Chatterjee

et al. 2021

Modern Techniques of Spectroscopy

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The role of ultrafast structural dynamics with physical and chemical changes in polydimethylsiloxane thin films by two-dimensional IR spectroscopy

Olson

Massari

2021

The Journal of Chemical Physics

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Fourier transform infrared (FTIR) and two-dimensional IR (2D-IR) spectroscopies were applied to polydimethylsiloxane (PDMS) cross-linked elastomer films. The vibrational probe for the systems studied was a silicon hydride mode that was covalently bound to the polymer chains. The structure and dynamics reported by this mode were measured in response to a wide range of chemical and physical perturbations, including elevated curing temperature, increased curing agent concentration, mechanical compression, and cooling to near the glass transition temperature. The FTIR spectra were found to be relatively insensitive to all of these perturbations, and 2D-IR spectroscopy revealed that this was due to the overwhelming influence of heterogeneity on the spectral line shape. Surprisingly, the deconvoluted spectral line shapes showed that there were only slight differences in the heterogeneous and homogeneous dynamics even with the drastic macroscopic changes occurring in different systems. In the context of modeling polymer behavior, the results confirm that dynamics on the ultrafast time scale need not be included to properly model PDMS elasticity.

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Influence of Solvent Swelling on Ultrafast Structural Dynamics in Polydimethylsiloxane Thin Films by Two-Dimensional IR Spectroscopy

Cited by 3 publications

References 77 publications

Vibrational Probe of the Structural Origins of Slow Recombination in Halide Perovskites

Vibrational Probe of the Structural Origins of Slow Recombination in Halide Perovskites

Two Dimensional Infrared Spectroscopy: A Structure Sensitive Technique with Ultrafast Time Resolution

The role of ultrafast structural dynamics with physical and chemical changes in polydimethylsiloxane thin films by two-dimensional IR spectroscopy

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