Seminário com o Prof. Heinz von Seggern – Colour-tuneable organic light-emitting transistors – 13 de setembro de 2013 – 10 horas
O PROGRAMA DE PÓS-GRADUAÇÃO EM FÍSICA convida para o seminário:
Colour-tuneable organic light-emitting transistors*
Prof. Heinz von Seggern
Electronic Materials, Technische Universität Darmstadt, 64287 Darmstadt, Germany.
*Presença obrigatória para os alunos matriculados na disciplina seminários
Resumo:
The unique property of ambipolar organic light emitting field-effect transistors (OLETs) is the ability to position the light emission zone within the transistor channel through the applied biases. In this talk the basics of the ambipolar OLET will be discussed and two examples for colour conversion will be demonstrated. Both approaches take advantage of the ability of a controlled displacement of the recombination zone through the organic semiconductors. In the first approach two different acenes with different emission colours are employed in a parallel stack in a top-contact bottom-gate FET configuration. It will be demonstrated that due to thermionic emission of electrons at the source, light of one colour can be generated near the source contact even in hole accumulation. Due to the electrically controllable positioning the charge carrier recombination zone can be directed from the top acene layer to in the bottom acene layer. Thereby the emitted light can be continuously shifted by about 50 nm from green to red. A second approach takes advantage of the horizontal displacement of the recombination zone within the channel of the transistor. On top of the semi-transparent gate electrode of a F8BT transistor a colour conversion layer is deposited in a wedge-like shape partially covering the channel. In the ambipolar regime the charge carrier recombination takes place in the F8BT layer, and dependent on the position of the recombination zone either the emitted light of the F8BT layer or the partially absorbed and converted light from the colour conversion layer can be detected. The electroluminescence maximum of the emitted light can be shifted by about 30 nm. The physics and potential applications of such colour tuneable OLETs will be discussed.
