The use of ultrathin substrates in organic electronics is enabling a wide range of applications for healthcare and wearable devices. Therefore, organic electronic circuits are very interesting for the development of real applications such as sensors readout. The advantage is represented by the possibility to realize electronics on ultrathin, flexible and transparent substrates with high throughput techniques inherited from graphical arts, among which ink-jet printing, bar coating and spray coating.
Here, we report on the fabrication of organic fully-printed and all-polymer complementary organic field-effect transistors (OFETs) and circuits like inverters and ring-oscillators on 1.4 μm ultrathin substrates. The process is then optimized to guarantee good charge transport and good OFET performances by performing the fabrication at room-temperature. The resulting devices demonstrate the robustness of the implemented approach, allowing good circuit performance also after deep stretching.
For the discrete devices fabrication we adopted a top-gate bottom-contact (TG/BC) OFET structure with PEDOT:PSS ink-jet printed source and drain electrodes. We used ink-jet printing to pattern the semiconductors with poly{[N,N9-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]
-alt-5,59-(2,29-bithiophene)} (P(NDI2OD-T2)) as n-type and diketopyrrolopyrrole-thieno[3,2-b]thiophene (DPPT-TT) as p-type; proper process optimization resulted in balanced mobilities. Poly(methyl-metacrylate) as dielectric was bar-coated and PEDOT:PSS gate electrode was ink-jet printed. A further coating layer was then deposited to further increase the device resistance to stretchability. The overall process results to be roll-to-rool compatible.
The present work demonstrates the possibility to produce fully-printed and transparent electronics building blocks for future complementary integrated circuits, thus benefiting of the high robustness of the complementary approach, onto an ultrathin skin-like substrate.