Achieving Bright, Low Voltage Emission Across the Spectrum with a Generic Electroluminescent Device

We have developed a generic electroluminescent device that can be used to generate and study electroluminescence (EL) from arbitrary luminescent materials, such as small molecules, conjugated polymers, quantum dots and more. The device has a metal-oxide-semiconductor capacitor structure with a carbon nanotube network contact and is operated by applying alternating current voltage. Unlike conventional light-emitting devices, our device can produce EL from materials with a variety of physical forms, chemical compositions and optoelectronic properties. The device relies on transient band bending at the source contact, which obviates the need for energy level alignment and enables emission from materials across a wide range of band gaps. By studying how device and material parameters affect device performance, we show how low voltage, efficient emission can be achieved. EL is observed at voltages near the optical gap of various emissive materials when a high-k gate oxide is used. Furthermore, bright EL can be obtained even in materials with large film thicknesses or extremely low carrier mobilities by tuning the carbon nanotube network density. Finally, the device can be driven resonantly to reduce the conventionally high input voltages. These results elucidate the performance limits of an electroluminescent device based on alternating carrier injection from a single contact and inform the capabilities of our device as a platform for new optoelectronic applications.