BACKGROUND:  Due to recent advances in materials technology, organic electronic devices are proven for applications as light emitting diodes, solar cells and active electronics devices. Compounds such as Cu-TCNQ, K-TCNQ and thin films containing fine participles of conductive materials embedded in low conductive organics have exhibited bistability. However, these materials have the problem of having only 2 light emission states. It is not possible to achieve gradation for a single pixel, which is required for many displays. Moreover, electrical resistance of the light emitter increases with operating time. Hence, it is desirable for the drive current to be constant to extend light emission lifetime. This cannot be done with current driving methods.

INNOVATION:  The innovation provides a means for controlling the current flowing through the device, whereby pixel light emission state gradation and constant current control become possible. The resistance value of the 'on' state is controlled by the amount of accumulated charge in the device by modulating the value of the switching voltage or the pulse width. The innovation lies in the composition of the device (chemistry and fabrication) an application of voltage, namely voltage value and pulse width.

DEVELOPMENT-TO-DATE:  Three devices have been manufactured using standard techniques such as vacuum deposition, spin-coating and dipping. Other techniques such as ink-jet are contemplated. One device was composed of a carbonitrile bistable layer, a fine metal particle dispersion layer and another carbonitrile bistable layer. The composite was sandwiched between aluminum electrodes and deposited on a glass substrate. A second device used aluminum quinoline was the organic bistable material. The third device used quinomethane as the bistable layer and gold was used for the electrode layers. Each device was tested at room temperature, using different voltages and pulse widths. In each case, the current value in the 'on' state rises in accordance with, and thus can be controlled through, voltage value or pulse width of the switching pulse. Chemical composition, layer thickness, applied voltage and pulse width are the subject of this invention.

ABOUT THE LAB:  This innovation is generated by the YY Labs at UCLA which is involved in a wide range of research involving conjugated polymers and their applications in (opto)electronic devices, such as light-emitting diodes, photodiodes, and field effect transistors. The lab emphasizes the study of the metal/polymer interface, invention of newer fabrication technologies and fabrication of flexible optoelectronic devices. The web site for the lab is, http://www.seas.ucla.edu/yylabs/.

Reference: UCLA Case No. 2004-285

PCT Application: PCT/US05/008478