We have recently developed a simple device that can be used to generate and study electroluminescence (EL) from arbitrary materials. The device has a metal-oxide-semiconductor capacitor structure and is operated by applying alternating current voltage to a carbon nanotube network source contact. Unlike conventional light-emitting devices, our device can produce EL from molecular materials with a variety of forms and optoelectronic properties, and EL can be measured during or immediately after deposition of the emissive material. However, alternating current devices are known to suffer from high operating voltages and poor efficiencies, hindering their practical usage. Here we illustrate how low voltage, efficient emission can be achieved with our device, using experiments and simulations to study how device and material parameters affect device performance. By using a thin high-k gate oxide layer, EL is observed at voltages near the optical gap of various emissive materials, which range from quantum dots to conjugated polymers to coordination complexes. Transient band bending at the source contact obviates the need for energy level alignment and allows for emission from narrow to wide band gap materials. Furthermore, device efficiency is improved by optimizing the sparsity of the carbon nanotube network depending on charge transport properties of the emitting material. Internally efficient EL can be theoretically achieved even in materials with extremely low carrier mobilities and large film thicknesses. These results elucidate the performance limits of a light-emitting device based on alternating carrier injection from a single contact and inform the capabilities of our device in new applications like electroluminescence spectroscopy.

Achieving low voltage, efficient emission with a generic alternating current electroluminescent device

ACS Spring Meeting 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.