cfaed Seminar Series

Potential applications of organic thin-film transistors (TFTs) are flexible sensors, bendable
displays, and integrated circuits on unconventional substrates, e.g., electronic anti-counterfeiting
features on banknotes. For these applications, the TFTs must meet a number of
requirements, such as low-voltage operation, good shelf-life stability and high switching
frequencies.
The first part of the talk will be dedicated to organic TFTs on flexible plastic and paper
substrates based on the high-mobility small-molecule organic semiconductor DNTT and its
didecyl and diphenyl derivatives C10-DNTT and DPh-DNTT. TFTs with channel lengths ranging
from 100 μm down to 0.5 μm have been fabricated using high-resolution silicon stencil masks
and low-voltage operation (3V) has been enabled by a very thin gate dielectric consisting of a
thin AlOx layer and a self-assembled monolayer (SAM) of an alkylphosphonic acid. For 11-stage
unipolar and complementary ring oscillators on plastic substrates, signal propagation delays per
stage as short as 240 ns and 4.2 μs have been measured in ambient air at a supply voltage of 4 V.
Building on the recent technology advances in the area of flexible electronics, novel applications
scenarios can be explored. For example, a novel and attractive target are health-monitoring
devices interlinked with the human body, e.g. skin-like epidermal sensor sheets, artificial skin
on prosthetics and wearable electronics. To accommodate for deformations such as twisting
and stretching, these next-generation electronics need to be extremely stretchable. Therefore,
the next frontier is to merge mechanical and electrical requirements and realize not only flexible
but also reliable stretchable electronics that are compatible with the soft, curvilinear surfaces of
biological tissue. The second part of the talk will address stretchable electronic materials and
transistors that are studied at Stanford University. A special focus will be on the development
and characterization of printed, intrinsically stretchable interconnects that will be a key-component
for stretchable circuits.