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

• Published in: Dyes and pigments 2023-03, Vol.211, p.111093, Article 111093
• Main Authors: Hong, Seung Hwa, Kim, Dong Won, Park, Soo Young
• Format: Article
• Language: English
• Subjects: Aqueous-alcohol-processable organic field effect transistors; Ethanol water cosolvent; Green solvent processing; Oligo(ethylene glycol) (OEG) side chains
• ISSN: 0143-7208; 1873-3743
• DOI: 10.1016/j.dyepig.2023.111093

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 × 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. •The flexible penta-ethylene glycol side chains could provide sufficient solubility in alcohol (ethanol) solvent.•PEG-IDIDF exhibited highly ordered structures in the film state when a process with ethanol:water cosolvent.•PEG-IDIDF based OFETs processed by the ethanol:water cosolvent showed high hole mobility.