Tuning Optoelectronic Properties of Ambipolar Organic Light‐ Emitting Transistors Using a Bulk‐Heterojunction Approach

Abstract

Bulk‐heterojunction engineering is demonstrated as an approach to producing ambipolar organic light‐emitting field‐effect transistors with tunable electrical and optoelectronic characteristics. The electron and hole mobilities, as well as the electroluminescence intensity, can be tuned over a large range by changing the composition of a bimolecular mixture consisting of α‐quinquethiophene and N,N′‐ditridecylperylene‐3,4,9,10‐tetracarboxylic‐diimide. Time‐resolved photoluminescence spectroscopy reveals that the phase segregation of the two molecules in the bulk heterojunction and their electronic interaction determine the optoelectronic properties of the devices. The results presented show that the bulk‐heterojunction approach, which is widely used in organic photovoltaic cells, can be successfully employed to select and tailor the functionality of field‐effect devices, including ambipolar charge transport and light emission.

Ambipolar organic semiconductor blends for photovoltaic cells

“…CuPc and C 60 ). [12][13][14] This effect indicates that percolation or grain boundaries are the limiting factors for charge transport in the analysed blends of molecular organic semiconductors. The different charge carrier types are transported in the respective transport material and by mixing the hopping distance between the molecules or the grains increases.…”

Efficient Top‐Gate, Ambipolar, Light‐Emitting Field‐Effect Transistors Based on a Green‐Light‐Emitting Polyfluorene

“…A similar device structure, also based on the use of a trap-free dielectric, was recently employed by Swensen et al [14] to show ambipolar transport and light emission in a polymer transistor. Other ambipolar lightemitting transistors have been demonstrated with blends [15,16] and bilayers [17,18] of evaporated p-and n-type materials, however, without spatial resolution or without free control of the recombination zone. Another promising route to ambipolar transistors are narrow bandgap organic semiconductors, [19,20] although these emit in the near-IR region and show intrinsically low electroluminescence efficiencies.…”

Near‐Infrared Light‐Emitting Ambipolar Organic Field‐Effect Transistors

“…[3][4][5][6][7][8] Only recently light emission from within the transistor channel was demonstrated in ambipolar OFETs (i.e., capable of transporting both holes and electrons). [9][10][11][12][13][14] In an ambipolar LEOFET when the gate is biased in between the source and drain potentials, holes and electrons are injected simultaneously at the opposite ends of the channel. At the point where the local potential within the channel equals the gate potential a pn-junction is formed at which opposite carriers can recombine to form excitons.…”