Exciton and Electron Traps on Structural Defects in Molecular Crystals with Dipolar Molecules

Izvekov, S. V.; Sugakov, V. I.

doi:10.1002/pssb.2221910217

Cited by 5 publications

(1 citation statement)

References 8 publications

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“…There exists a variety of structural defects that cause variations from the ideality . Chemical defects arise from substitutional molecules or physical defects because of the distortion of periodic lattices like vacancies, dislocation lines, or stacking faults. , Optical properties as well as charge transport within organic semiconductors are highly affected by defects. − Structural defects at a considerably larger length scales are the crystal size and crystal mosaicity associated with grain boundaries between single-crystalline domains …”

Section: Introductionmentioning

confidence: 99%

Molecular Disorder in Crystalline Thin Films of an Asymmetric BTBT Derivative

et al. 2021

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The molecule 2-decyl-7-phenyl-[1]benzothieno[3,2-b][1]benzothiophene (Ph-BTBT-10) is an organic semiconductor with outstanding performance in thin-film transistors. The asymmetric shape of the molecule causes an unusual phase behavior, which is a result of a distinct difference in the molecular arrangement between the head-to-head stacking of the molecules versus head-to-tail stacking. Thin films are prepared at elevated temperatures by crystallization from melt under controlled cooling rates, thermal-gradient crystallization, and bar coating at elevated temperatures. The films are investigated using X-ray diffraction techniques. Unusual peak-broadening effects are found, which cannot be explained using standard models. The modeling of the diffraction patterns with a statistic variation of the molecules reveal that a specific type of molecular disorder is responsible for the observed peak-broadening phenomena: the known head-to-head stacking within the crystalline phase is disturbed by the statistic integration of reversed (or flipped) molecules. It is found that 7–15% of the molecules are integrated in a reversed way, and these fractions are correlated with cooling rates during the sample preparation procedure. Temperature-dependent in situ experiments reveal that the defects can be healed by approaching the transition from the crystalline state to the smectic E state at a temperature of 145 °C. This work identifies and quantifies a specific crystalline defect type within thin films of an asymmetric rodlike conjugated molecule, which is caused by the crystallization kinetics.

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