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Vibrational Neutron Spectroscopy Data for Small Molecule Organic Semiconductors

Citation

Harrelson, Thomas; Dantanarayana, Varuni; Faller, Roland; Moule, Adam (2017), Vibrational Neutron Spectroscopy Data for Small Molecule Organic Semiconductors, Dryad, Dataset, https://doi.org/10.25338/B81015

Abstract

Organic semiconductors are a class of molecules that self-assemble into materials that have semiconducting properties. Recently, they have generated a large amount of research interest due to their solution processability, mechanical flexibility, and conducting properties. Small molecule organic semiconductors are highly crystalline, which means molecular vibrations/phonons are the dominant factors affecting charge transport properties. A key to improving small-molecule semiconductors involves designing materials that minimize the effects of vibrations/phonons on charge transport. Vibrational neutron spectroscopy is a method for characterizing molecular vibrations and phonon modes over a wide energy range (1 meV - 1 eV). Each of the peaks represent the frequency of the motion of hydrogens present in the material. The data was collected at 5 K. Here we present vibrational neutron spectroscopy data for the small molecule organic semiconductors: BTBT, c8-BTBT, m8-BTBT, TIPS-pentacene, TIPS-ADT, and TES-ADT. This data can be used to accurately find the vibrational modes affecting charge transport.

Methods

The data was collected by cooling the sample to ~5 K, then opening the shutter allowing pulses of neutrons to interact with the sample at known time points. Scattering neutrons hit the analyzer crystals, which only reflect scattered neutrons with a known wavelength toward the detector. The detector records the time at which a scattered neutron hits the detector, allowing the energy loss of the scattered neutron to be calculated through time-of-flight analysis. The sample was run long enough to sufficiently reduce the signal to noise ratio. The data is displayed in 3 columns: Energy loss (in meV), Intensity, error. Each text file contains 3 sets of data: the first one is the results from the forward scattering analyzers, the second from the back scattering analyzers, and the third is the average of the first two. The forward scattering data comes from low momentum transfer scattering events, and the back scattering data comes from high momentum transfer scattering events.

Usage Notes

File format is detailed above, but we stress that care should be taken when attempting to compare forward scattering and back scattering results. In most samples, no physical intuition can be gained from such a comparison; the comparison serves as a quality control for the experimental run. 

Funding

Department of Energy - Basic Energy Sciences, Award: DE-SC0010419