Highly Conductive Inkjet-Printed PEDOT:PSS Film under Cyclic Stretching

Inkjet-printed conductive polymer PEDOT:PSS films have provided a new developing direction for realizing the stretchable transparent electrodes in optoelectronic devices. However, their conductivity and stretchability are limited as the presence of insulating PSS chains, rigid PEDOT conjugated backbone, and stronger inter-chain interactions in the pristine polymer, respectively. Here, we report a PEDOT:PSS film with preferable electrical and mechanical performances by inkjet-printing the formulated printable ink containing PEDOT:PSS, formamide (FA), d-sorbitol (SOR), sodium dodecyl benzene sulfonate (DBSS), and ethylene glycol (EG). The inkjet-printed uniform PEDOT:PSS film exhibits a high conductivity of 1050 S/cm and sheet resistance of less than 145 Ω/sq on both rigid and flexible substrates. Moreover, the resistance can remain stable after 200 cycles of stretching at 55% strain. The film also presents good stability during repetitive stretching-releasing cycles. The significantly enhanced conductivity of the film lies on the conformational transition of the backbone by secondary doping and post-treatment with FA as well as removing the excess PSS components after phase separation between PEDOT and PSS. Meanwhile, SOR serves as a plasticizer to break the original hydrogen bonds between PSSH chains and provides larger free volume for polymer chain extension, which gives the PEDOT:PSS film the ability to tolerant cyclic tension. This is one of the optimal performances currently reported for inkjet-printed stretchable PEDOT:PSS films. The inkjet-printed PEDOT:PSS film with high conductivity, stretching properties, as well as good biocompatibility exhibits promising prospects as anodes on optoelectronic devices.