In-plane light emission of organic light-emitting transistors with bilayer structure using ambipolar semiconducting polymers

• Bilayer structure using ambipolar semiconducting polymers.
• Organic light-emitting transistors with bilayer structure are fabricated.
• Hole and electron transport occur mainly along the different organic layers.
• In-plane recombination zone of electrons and holes exists near the bilayer interface.
• For bilayer device, in-plane light-emitting pattern is achieved.

The concept of using an ambipolar bilayer semiconducting heterostructure in organic light-emitting transistors (OLETs) is introduced to provide a new approach to achieve surface emission. The properties of top-gate-type bilayer OLETs with ambipolar materials based on two types of fluorene-type polymers used as an emissive layer and an electron blocking layer are investigated. Line-shaped yellow–green emission occurs near a hole-injection electrode. When hole transport is dominant in the upper layer which acts as an electron blocking layer, and electrons are injected into the lower layer, an in-plane light-emitting pattern is observed. The measured in-plane emission zone confirms that both hole and electron transport are determined to occur mainly along the different organic layers between the source and drain electrodes, and an in-plane recombination zone of electrons and holes exists near the bilayer organic interface. This work is anticipated to be useful for the development of in-plane light-emitting transistors.

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