The impact of film deposition and annealing on the nanostructure and dielectric constant of organic semiconductor thin films

Abstract

Different processing conditions lead to a range of molecular packing motifs for films of a novel organic semiconductor, which enables tuning of the optical frequency dielectric constant.

The Effect of Fluorinated Benzothiadiazole-dicyanovinyl Acceptors on the Dielectric Constants of Organic Photovoltaic Materials

“…The scattering profiles measured using GIXRD on the thermally treated films show a peak at 7.0° corresponding to a packing distance of 12.6 Å. This peak is consistent with the packing distance of the glycolated side chains reported for other chromophores with the same glycol chains attached . A similar morphology change was observed for each of the monomeric materials when aged at room temperature.…”

“…This peak is consistent with the packing distance of the glycolated side chains reported for other chromophores with the same glycol chains attached. 27 A similar morphology change was observed for each of the monomeric materials when aged at room temperature. For example, a thin film of CPDT-DFBT-DCV when left under nitrogen for 24 h at room temperature had the same peak at 7°in the GIXRD profile (Figure S25).…”

“…For example, one study showed that films formed by thermal evaporation possessed a higher ε opt compared to films of the same material prepared by solution processing. 27 In a previous study, it was reported that an A-D-D-A compound with glycol solubilizing groups, A being dicyanovinyl benzothiadiazole moieties and D composed of cyclopentadithiophene units, had an ε opt = 4.6, which was the highest reported at the time. 28 Given that fluorine atoms are regularly attached to organic semiconductor materials used in the most efficient BHJ OPV devices and have been shown to increase the low frequency (kHz−MHz) dielectric constant, we were interested to investigate their effect on the optical frequency dielectric constant of the previously reported A-D-D-A compound.…”

“…Furthermore, different processing methods can lead to differences in the optical frequency dielectric constant for the same chromophore. For example, one study showed that films formed by thermal evaporation possessed a higher ε opt compared to films of the same material prepared by solution processing …”

The effect of fluorination on the low and high frequency dielectric constants of non-polymeric organic semiconductors – towards homojunction solar cells

“…S1–S24). The syntheses of the protonated 7-bromo-benzo[ c ][1,2,5]thiadiazole-4-carbaldehyde, 9 , 33 10 , 42 protonated CPDT-BT-Ald 33 and D(CPDT-BT-Ald) 34 have been previously reported. However, while 8 is a reported compound, 43 we were unable to repeat the results for some of the described steps.…”