Inverted Tandem OLEDs with Independent Drive Circuitry
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Solution Overview
Problem
Conventional OLEDs experience color shift issues due to imbalances in charge carriers, particularly in phosphorescent devices, which affect the consistency of light emission across different current densities.
Innovation Solution
An inverted tandem structure is implemented, where two OLEDs share a common electrode, with independent drive circuitry to control each layer, separating phosphorescent blue and red/green emitters, and using a transparent cathode between reflective anodes to minimize color shift and achieve stable white light emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If phosphorescent emitters are used in conventional OLEDs, then light emission efficiency is improved, but color shift occurs due to charge carrier imbalance
Solution Approach 1:
The patent divides the single phosphorescent emitter into multiple separate emitters (blue phosphorescent emitter and red/green phosphorescent emitters) that are stacked in an inverted tandem configuration. Each emitter is independently controlled by separate drive circuitry, allowing independent optimization of charge carrier balance for each emitter, thereby eliminating color shift while maintaining high light emission efficiency through phosphorescence.
2Device complexity
If a single electrode structure is used, then device simplicity is maintained, but independent control of multiple emitters is not achieved
Solution Approach 1:
The patent merges multiple emitters into a single stacked device structure where blue phosphorescent emitter and red/green phosphorescent emitters are combined in an inverted tandem configuration. The emitters share a common substrate and encapsulation structure, but each emitter has its own drive circuitry for independent control, achieving both structural integration and operational independence.
3Ease of manufacture
If conventional OLED structure is used, then manufacturing process is simple, but color shift at gray levels occurs
Solution Approach 1:
The patent implements dynamic independent control of multiple emitters through separate drive circuitry for each phosphorescent emitter. This allows dynamic adjustment of drive currents to each emitter to maintain optimal charge carrier balance across different gray levels, eliminating color shift while preserving manufacturing simplicity through the stacked inverted tandem structure that uses standard OLED fabrication processes.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively reduces and eliminates color shift at gray levels, providing consistent white light emission by independent control of each OLED layer, enhancing the stability and accuracy of light output in OLED devices.
Implementation Method 1
An electric current is applied across the device, causing negatively charged electrons to move into the organic material(s) from the cathode. Positive charges, typically referred to as holes, move in from the anode. The positive and negative charges meet in the center layers (i.e., the semiconducting organic material), combine, and produce photons.
Implementation Method 2
The two OLEDs have a reflective anode on one side and a transparent anode on the other side adjacent to a glass substrate.
Data Source
AI summary
An OLED apparatus is provided that includes a first electrode having a first polarity, and an electrode arrangement spaced apart from the first electrode and having a second polarity. The OLED apparatus also includes a first organic emissive layer interposed between the first electrode and the electrode arrangement, and a second electrode spaced apart from the electrode arrangement in a direction opposite the first electrode. The second electrode has the first polarity. The OLED apparatus further includes a second organic emissive layer interposed between the second electrode and the electrode arrangement, and a drive circuit for providing a first energizing signal to the first electrode and the electrode arrangement and a second energizing signal to the second electrode and the electrode arrangement. A method for manufacturing an OLED array is provided.