Air-stable polymer organic thin-film transistors by solution-processed encapsulation

The air- and encapsulation-induced degradations of poly(3-hexylthiophene) (P3HT) organic thin-film transistors (OTFTs) encapsulated with solution-processed polymer films were systematically analyzed to realize air-stable devices. By studying the potential degradation-inducing factors from air–O2, moisture, N2, and light, we determined that device degradations could be eliminated by isolating the devices from two of the factors: moisture and light. In terms of encapsulation-induced degradations, we examined 10 types of encapsulating polymers and found that such degradations could be avoided with polymers containing low-polarity function groups, including poly(vinyl methyl ketone), poly(methyl vinyl ether), poly(methyl methacrylate), and polystyrene. Based upon the identified sources of degradations, we demonstrated an encapsulation approach that involved (1) using a low-polarity encapsulating polymer layer to serve as a moisture barrier and to avoid encapsulation-induced degradation, and (2) applying a light-blocking agent. The resultant OTFTs showed no encapsulation-induced degradation while maintaining stable device characteristics for >5500 h of storage in the ambient air.

Solution-processed polymer encapsulation is developed for poly(3-hexylthiophene) (P3HT) organic thin-film transistors (OTFTs) to achieve air-stable devices. Various sources of device degradation, including O2, H2O, light, encapsulating polymer, and solvent, are systematically analyzed. Based upon the identified sources of degradations, an effective encapsulation approach is demonstrated, which enables P3HT OTFTs to remain stable for > 5500 h in air.Figure optionsDownload as PowerPoint slideResearch highlights
► Moisture induces recoverable p-type doping effects on P3HT OTFTs irrespective of the presence of light.
► Oxygen causes no degradation to P3HT OTFTs without light, but induces irrecoverable degradations with light.
► Encapsulation-induced degradation to P3HT OTFTs depends upon the polarity of the encapsulating polymer, and can be avoided with low-polarity polymers.
► Encapsulating P3HT OTFTs with a low-polarity polymer and a light-blocking agent achieves air-stability for >5500 h.