Solution processed highly stretchable organic electronic device systems

Nowadays, stretchable electronics are emerging and of growing interest. Their stretchability and conformability to irregular and movable surface compared with conventional rigid electronics greatly increase their applications in wearable devices, soft robotics, medical treatments, skin display and energy storage systems. So far, there are two general approaches to realize stretchable electronics. One is by combining rigid and non-stretchable electronic units with elastic interconnects. However, this structural engineering strategy will require complicated fabrication processes, and will potentially sacrifice active device density and integrated strain tolerance. Another approach is by utilizing intrinsically highly stretchable materials to construct all the device constituents, ensuring high device coverage density and desirable integrated stretchability. There are two major difficulties in enabling intrinsically highly stretchable electronics. One is to find new materials which possess both high stretchability and desired electrical performance. On the other hand, a suitable fabrication platform needs to be developed, as most of the polymer-based stretchable electronics materials are incompatible with standard photolithography microfabrication flows. This dissertation describes material preparation and solution-process as method for fully stretchable electronic device systems. In first part of this thesis, stretchable p-type organic semiconductor was enabled by azide-crosslinking, and p-type organic thin-film field-effect transistor (TFT) was fabricated by inkjet-printing with stretchability of 100% strain and an average mobility of 0.56 cm2V-1s-1. A fluorinated polymer as dielectric thin film was studied. This part of work demonstrated the world's first inkjet-printed fully stretchable TFT array. In second part of this thesis, stretchable n-type organic semiconductor was enabled by nanoconfinement effect， and n-type TFT was developed with stretchability of 100% strain and an average mobility of 0.112 cm2V-1s-1. Nanoconfinement effect on n-channel organic semiconductor material was studied. This part of work demonstrated the world first fully stretchable n-type TFT array with mobility higher than 0.1 cm2V-1s-1. In third part of this thesis, p-type TFT was combined with n-type as the world first fully stretchable complementary inverter circuit with stretchability of 100% strain and an amplification number of 14.7. In the last part of this work, a fully stretchable polymer-based light-emitting electrochemical cell was developed and was integrated with TFT array as the world's first fully stretchable active-matrix light-emitting array. The final integrated device possessed stretchability of 30% strain without luminescence degradation. Overall, this dissertation presents the developments of fully stretchable electronics and achieves first demonstrations of fully stretchable complementary inverter circuit and active-matrix light emitting cell. The methodologies include the preparation of related materials, compatible fabrication strategies and device systems integrations. With increasing demand of soft electronics in both academia and industry, this work contributes guidelines for the future research of solution processed polymer-based electronics and their advanced integrations and application

Keywords: Materials Science and Engineering.
Advisor: Bao Zhenan
Dauskardt R. H. (Reinhold H.)
Appel Eric (Eric Andrew)