Efficient energy transfer in organic light-emitting transistor with tunable wavelength

Key challenges in the development of organic light-emitting transistors (OLETs) are blocking both scientific research and practical applications of these devices, e.g., the absence of high-mobility emissive organic semiconductor materials, low device efficiency, and color tunability. Here, we report a novel device configuration called the energy transfer organic light-emitting transistor (ET-OLET) that is intended to overcome these challenges. An organic fluorescent dye-doped polymethyl methacrylate (PMMA) layer is inserted below the conventional high-mobility organic semiconductor layer in a single-component OLET to separate the functions of the charge transport and light-emitting layers, thus making the challenge to essentially integrate the high mobility and emissive functions within a single organic semiconductor in a conventional OLET or multilayer OLET unnecessary. In this architecture, there is little change in mobility, but the external quantum efficiency (EQE) of the ET-OLET is more than six times that of the conventional OLET because of the efficient Förster resonance energy transfer, which avoids exciton-charge annihilation. In addition, the emission color can be tuned from blue to white to green-yellow using the source-drain and gate voltages. The proposed structure is promising for use with electrically pumped organic lasers.