We demonstrated the effect of a buffer layer on the electrical characteristics of ferroelectric polymer capacitors and field-effect transistors. Various polymer materials with a dielectric constant between 2 and 42 were used to form buffer layers with a similar thicknesses, but with different capacitances. In order to evaluate the characteristics of the ferroelectrics with a buffer layer, the polarization–voltage characteristics of the capacitor, the transfer characteristics, and the retention characteristics of the transistors were investigated. As the capacitance of the buffer layer increased, high remnant polarization (Pr), high hysteresis, and long retention times were observed. Exceptionally, when poly(methylmethacrylate) and rigid poly(aryl ether) (poly(9,9-bis(4-hydroxyphenyl)fluorene-co-decafluorobiphenyl)) were used as the buffer layer, Pr had a value close to 0 in the dynamic measurement polarization–voltage (P–V) characteristic, but the quasi-static measurement transfer characteristic and the static measurement retention characteristic showed relatively high hysteresis and long retention times. Our study provides a scientific and technical basis for the design of ferroelectric memory and neuromorphic devices.
We systematically investigated the mechanism of subtractive
contact
patterning (SCP) and demonstrated high-resolution organic light-emitting
diodes (OLEDs) using this SCP process. Owing to the application of
the SCP process to various types of organic semiconducting thin films,
crystalline thin films (e.g., pentacene) generated patterns via the
delamination mechanism and amorphous small molecule thin films (e.g.,
tris(8-hydroxyquinolinato)aluminum) generated patterns via the
diffusion mechanism. In the pattern generation via diffusion, we reported
that the higher the processing temperature and the longer the processing
time were, the deeper was the pattern depth. In particular, the patterning
speed was proportional to the temperature in an exponential function.
SCP can be applied to doped small molecule-based thin films and limitedly
applied to polymer thin films. Finally, a high-resolution OLED pattern
of less than 10 μm wide was fabricated by applying the SCP process
without any detrimental effects on the device performance. Furthermore,
this SCP process was applied to flexible and curved thin films, which
verified its potential use for roll-to-roll processes. This study
provides a scientific and technological basis for the fabrication
of high-resolution patterns of organic electronic devices such as
OLEDs.
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