High-brightness low voltage alternative current electroluminescent devices for human wearable displays

Due to their high contrast, low cost, simple preparation and low energy consumption, alternative current electroluminescence (ACEL) devices are ideal for information display in wearable electronic systems. However, ACEL displays require high driving voltage normally above 100 V. Achieving high brightness at human-safety driving voltage in ACEL devices remains a challenge. In this study a new field enhancement strategy has been developed by doping the bottom dielectric layer with materials that have a high permittivity. In this way, the electric field can be concentrated in the luminescent layer and the charge separation of the ZnS/Cu powders can be improved, which helps to lower the driving voltage of ACEL while achieving high brightness of light emission. A high brightness of 175.2 cd/m 2 was obtained at the human-safety voltage of 35 V, The brightness can reach 1448.3 cd/m 2 at 110 V. The field enhancement strategy can be implemented by simple screen-printing process and the ACEL can be made on a fabric substrate with mechanical cyclic durability. As a demonstrator of human wearable display, the ACEL was integrated with a temperature sensing system to detect and display human body temperature in real time in both static and dynamic modes.