Third Electrode Carrier Release for EL Device Stability
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Solution Overview
Problem
EL elements experience performance degradation due to excess carrier accumulation at the interface between the light-emitting layer and the carrier transport layer, which existing techniques do not effectively address.
Innovation Solution
A light-emitting device configuration that includes a first electrode, a light-emitting layer, and a second electrode, with a charge transport layer between the electrodes and a third electrode that overlaps the light-emitting layer, allowing for controlled carrier release through a drive circuit with switches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional EL element structure without a third electrode is used, then the device structure is simple, but excess carriers accumulate at the interface between the light-emitting layer and carrier transport layer, causing performance degradation
Solution Approach 1:
The electrode structure is segmented by introducing a third electrode between the first electrode and the light-emitting layer. This segmentation allows independent control of carrier injection from different electrodes, enabling the release of excess carriers accumulated at the interface without compromising the overall device structure integrity.
Solution Approach 2:
The third electrode acts as an intermediary element that mediates carrier transport between the first electrode and the light-emitting layer. By positioning this intermediate electrode at the interface region, it facilitates the controlled release of excess carriers that would otherwise accumulate and degrade device performance.
2Duration of action of stationary object
If carrier injection is continuously maintained to sustain light emission, then the light-emitting device operates continuously, but excess carriers accumulate at the interface, reducing device lifetime
Solution Approach 1:
The driving method employs periodic switching between light emission mode and excess carrier release mode. During light emission mode, carriers are injected to sustain luminescence. During excess carrier release mode, the third electrode is activated to remove accumulated carriers. This periodic alternation prevents carrier accumulation and extends device lifetime while maintaining overall light emission productivity.
Solution Approach 2:
The system maintains continuous useful action by rapidly alternating between emission and carrier release cycles. The frequent switching ensures that carrier accumulation is continuously prevented, allowing the device to sustain light emission over extended periods without performance degradation from carrier buildup.
Data Source
AI summary
In a light-emitting device, a first electrode, a light-emitting layer, and a second electrode are disposed in the order recited. Moreover, a charge transport layer is disposed between the first electrode and the light-emitting layer and/or between the second electrode and the light-emitting layer. A third electrode at least partly overlaps the light-emitting layer. Moreover, the third electrode is disposed between the charge transport layer and the light-emitting layer.