The effect of gate dielectric deposition at different vacuum conditions on the field-effect mobility of pentacene based organic field effect transistors

Biring, Sajal; Li, Ya‐Ze; Lee, Chih‐Chien; Pan, An; Li, Yan-De; Kumar, Gautham; Liu, Shun‐Wei

doi:10.1016/j.tsf.2017.06.054

Cited by 6 publications

(1 citation statement)

References 32 publications

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“…As discussed in the Crystallography Section, the main type of intermolecular π–π stacking observed in crystals was T-shaped, with distances in the range for good charge transport. While T-shaped type interactions are not as good as S- and P-type interactions for charge transport, they can lead to high charge carrier mobility in some cases, provided the orbital overlap is large. , An example of a high-mobility material (up to 2.0 cm 2 V –1 s –1 ) with herringbone packing is pentacene, where the π–π interactions are T-shaped . To estimate the overlap integrals of our complexes, we performed single-point energy calculations of the molecular dimers.…”

Section: Resultsmentioning

confidence: 99%

Structure–Property Study of Homoleptic Zinc(II) Complexes of Di(arylethynyl) Azadipyrromethene as Nonfullerene Acceptors for Organic Photovoltaics: Effect of the Aryl Group

et al. 2020

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Azadipyrromethene-based zinc(II) complexes were demonstrated to be promising molecular organic semiconductors for electronic applications due to their easy preparation, tunable structures, and high electron affinity. The first successful such complex incorporated phenylethynyl groups at the pyrrolic positions, which red-shifted the absorption spectra of zinc(II) bis(tetraphenyl azadipyrromethene) and improved the morphology in blends with poly(3-hexylthiophene) (P3HT). We recently discovered that replacing the phenyl group in the pyrrolic positions with the larger 1-naphthyl group [Zn(L2) 2 ] increases the crystallinity and improves the organic photovoltaic (OPV) performance. In this work, two more aryl groups were explored to further investigate the relationship between the aryl groups in the pyrrolic position and electronic properties: naphthyl with a different anchoring site, 2-naphthyl [Zn(L3) 2 ], and a larger aryl group, 9phenanthrenyl [Zn(L4) 2 ]. The larger aryl group slightly improved the absorptivity, red-shifted the absorption spectra, and led to different packing modes in crystals with most intermolecular π−π stacking interactions being of T-shaped-type involving the pyrrolic aryl group of one complex. Of the series, 1-naphthyl gave the highest crystallinity. The organic photovoltaic (OPV) power conversion efficiency (PCE) of Zn(L3) 2 and Zn(L4) 2 when blended with P3HT was 3.7 and 3.4%, respectively, both lower than that of Zn(L2) 2 (PCE of 5.5%) due to the higher trap-assisted recombination and less favorable morphology. The charge carrier mobility in these complexes was also relatively low, also limiting the performance. Single-point energy calculations point to low overlap integrals as a cause for the low mobility. The aryl group anchoring position and size, therefore, have a large effect on the properties in these systems, but do not appear to significantly enhance intermolecular interactions.

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