Florian Eder

Organic electronics on paper

We have fabricated organic thin-film transistors and ring oscillators on paper and on flexible polyetherether ketone film using small-molecule hydrocarbon pentacene as the semiconductor and solution-processed polyvinylphenol as the gate dielectric. Transistors on paper have a carrier mobility of 0.2 cm2/V s and an on/off current ratio of 106, similar to devices on polyetherether ketone. A signal propagation delay of 22 μs per stage was measured for pentacene ring oscillators on polyetherether ketone film, and a signal delay of 12 ms was obtained for ring oscillators on paper.

Pentacene organic transistors and ring oscillators on glass and on flexible polymeric substrates

We have fabricated organic thin film transistors, inverters, and ring oscillators on glass and on flexible polyethylene naphthalate, using the small-molecule hydrocarbon pentacene as the semiconductor and solution-processed polyvinylphenol as the gate dielectric. Depending on the choice of substrate, the transistors have a carrier mobility between 0.3 and 0.7 cm2/V s, an on/off current ratio between 105 and 106, and a subthreshold swing between 0.9 and 1.6 V/decade. To account for the positive switch-on voltage of the transistors, circuits were designed to operate with integrated level shifting. Depending on the type of substrate, ring oscillators have a signal propagation delay as low as 15 μs per stage.

Flexible organic complementary circuits

We report the first organic complementary circuits on flexible substrates. Organic thin-film transistors were fabricated using pentacene as the semiconductor for the p-channel devices and hexadecafluorocopperphthalocyanine (F/sub 16/CuPc) as the semiconductor for the n-channel devices. Both semiconductors were purchased from commercial sources and deposited by evaporation in vacuum. The pentacene layer was photolithographically patterned to simplify the circuit layout and reduce the circuit area. The transistors and circuits were manufactured on thin, transparent sheets of polyethylene naphthalate. Evaporated metals were used to define all contacts and interconnects, and a 50-nm-thick layer of solution-processed polyvinylphenol was used as the gate dielectric. Transistors and circuits operate at supply voltages as low as 8 V, and ring oscillators have a signal propagation delay as low as 8 /spl mu/s per stage. To our knowledge, these are the fastest organic complementary circuits reported to date.