New TFEL devices show promise for HMDs

17 Jun 2002

Head-mounted displays small enough to fit into a visor in automobile, aircraft, and microsurgery environments won't be practical until the conversion of electricity into tiny parcels of light can be done using small currents and voltages. Now a new electroluminescent device by researchers at Georgia tech uses one-tenth the voltage of previous devices.

A new thin-film electroluminescent (TFEL) concept developed by Christopher Summers, chris.summers@gtri.gatech.edu) employs thinner insulating layers, which permits the electrons to reach their necessary velocity using much less voltage: 15-25 V instead of the customary 150-200 V. The efficiency of the new device is still low and the cost of growing the crystalline insulating layers is comparatively high, but the lower-voltage requirements, and the smaller circuitry this will permit, may make the approach worthwhile.

At the heart of a TFEL device is a host material such as ZnS doped with luminescing centers such as Mn atoms. On either side of this material are insulating layers which serve as suppliers of electrons. High electric fields, supplied by a voltage applied across the whole sandwich, launch electrons into the ZnS where they strike a manganese atom, which emits a photon.