Spatial control of the recombination zone in an ambipolar light-emitting organic transistor

Organic semiconductors show efficient electroluminescence which has led to their commercialization in light-emitting diodes, but has also raised fundamental questions about their recombination and emission physics. Organic ambipolar field-effect transistors can support both hole and electron transport at the semiconductor-dielectric interface. Using their ability to emit light owing to charge recombination within the transistor channel should enable new ways to study the recombination physics and realize new electrooptical devices. Here we demonstrate ambipolar light-emitting transistors based on a semiconducting polymer with both efficient electron and hole transport and good photoluminescence efficiency. In our device configuration, electrons and holes injected from separate calcium and gold electrodes recombine radiatively within the channel. We can move the recombination zone with the applied gate and source-drain bias to any position within the channel. This provides a direct visualization and proof of coexisting electron and hole accumulation layers in an ambipolar transport regime.