A generic electroluminescent device for emission from infrared to ultraviolet wavelengths

The range of luminescent materials that can be used in electroluminescent devices is limited due to material processing challenges and band alignment issues. This impedes the development of electroluminescent devices at extreme wavelengths and hinders the use of electroluminescence spectroscopy as an analytical technique. Here, we show that a two-terminal device that uses an array of carbon nanotubes as the source contact can excite electroluminescence from various materials independent of their chemical composition. Transient band bending, created by applying an a.c. gate voltage, is used to achieve charge injection across different band alignments. As a result, the device can produce electroluminescence from long-wave infrared (0.13 eV) to ultraviolet (3.3 eV) wavelengths depending on the emitting material drop-casted on top of the nanotube array, and with onset voltages approaching the optical energy gap of the emitting material. We show that our device can be used to probe a chemical reaction in a liquid droplet via electroluminescence spectroscopy and can be used as an electroluminescence sensor for detecting organic vapours.