Dual-function electroluminescent device and method for driving the same

Abstract

This invention relates to a method of driving a dual-function light-emitting and light-sensing device (5) comprising an organic electroluminescent layer (1), such as a polymer layer or a small molecule compound layer, which is sandwiched between a first and a second electrode (2,3), comprising the following steps:-applying, during a emission state (t1), a first emission signal (V1, J1) to said electroluminescent layer (1), said first signal being such that light is generated by and emitted from said electroluminescent layer (1), and-applying, during a sensing state (t2), a second driving signal (V2,J2) to said organic electroluminescent layer (1), said second driving signal being such that the power of said second driving signal has essentially a zero value for accurately detecting an electric current generated in said organic electroluminescent layer when said organic electroluminescent layer is hit by external light This invention also relates to a dual-function light-emitting and light-sensing device and applications thereof.

Description

technical field [0001] The present invention relates to a method of driving a bifunctional light-emitting and light-sensing device comprising an organic electroluminescent layer, such as a polymer layer or a small molecule compound layer, sandwiched between first and second electrodes. The invention also relates to a dual function light emitting and light sensing device. Furthermore, the invention relates to various applications of such displays. Background technique [0002] Organic electroluminescent displays and devices are a relatively newly discovered technology based on the recognition that certain organic materials, such as certain polymers, are used as semiconductors in light emitting diodes. These devices have attracted attention because the use of organic materials, such as polymeric materials, makes them light, flexible, and relatively inexpensive to manufacture. [0003] Recently, it has also been found that such a light-emitting device can be used as a tool fo...

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Problems solved by technology

[0004] However, the dual function diodes described above have many disadvantages

First, the device described in US-5,504,323 exhibits an asymmetric leakage current characteristic around 0V, and thus the leakage current was found to be unstable

Furthermore, the application of high negative voltage leads to an increased possibility of damage to the device, and the dark current is highly unstable as it is directly related to the damage and short circuit of the organic electroluminescent layer.

This results in a low signal-to-noise ratio for photocurrent detection in reverse operation

But, more importantly, existing devices consume a lot of energy due to the large drive voltage

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