Aqueous-alcohol-processable indolo[3,2-b]indole-based crystalline small molecules for organic field effect transistors with oligo(ethylene glycol) side chains

We address an eco-friendly aqueous process approach to obtain efficient/stable small molecule organic field effect transistors (OFETs). Penta-ethylene glycol (PEG) side chains were introduced at N-positions of the rigid backbone structures of indolo[3,2-b]indole(IDID), thus enabling the formation of PEG-IDIDF. The PEG-IDIDF exhibited remarkable solubility in alcohol (ethanol) solvent. The X-ray diffraction and grazing incidence wide angle X-ray scattering measurements indicate that the suitable addition of a typical cosolvent, water, to ethanol solvent significantly contributes to an enhancement in film crystallinity and molecular stacking orientation features than those of the PEG-IDIDF film processed by using a single solvent. Consequently, the PEG-IDIDF OFETs processed by the ethanol water cosolvent (90:10) ratio yielded the enhanced hole mobility of 4.07 x 10-3 cm2 V-1 s-1 and current on/off ratio of 106, which was one of the highest reliable mobility for small molecules OFETs processed with an alcohol solvent.

Automated summary

We propose an eco-friendly aqueous process to obtain efficient/stable small molecule organic field effect transistors (OFETs). Penta-ethylene glycol (PEG) side chains were introduced to the rigid backbone structures of indolo[3,2-b]indole(IDID), leading to the formation of PEG-IDIDF. The addition of water as a cosolvent significantly enhances the film crystallinity and molecular stacking orientation of PEG-IDIDF, resulting in improved hole mobility and current on/off ratio for the PEG-IDIDF OFETs processed with ethanol water cosolvent (90:10) ratio.