OLED Color Tuning via Pulsed Driving Mode Variation
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Solution Overview
Problem
OLED devices experience efficiency decreases and color alteration due to non-uniform aging, leading to undesirable effects such as decreased luminous efficacy and 'image sticking' when operated under constant DC current, as the charge balance and recombination rate profile across the emissive layer change.
Innovation Solution
Implementing non-DC driving schemes with varying current/voltage profiles to modify the recombination profile of OLED devices, allowing for partial recovery of efficiency losses and extending device lifetime, while minimizing image sticking effects by using waveforms that can change the recombination zone within the emissive layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If OLED devices are operated under constant DC current, then the operation is simple and stable, but efficiency decreases and color alteration occur due to non-uniform aging
Solution Approach 1:
The patent applies dynamics by transitioning from static DC current operation to dynamic pulsed current operation. The OLED device is driven with periodic pulses rather than constant current, allowing the recombination profile to be modulated over time. This dynamic operation enables the device to access different recombination zones sequentially, preventing the non-uniform aging that occurs under constant DC conditions and extending device lifetime while maintaining operational simplicity through automated waveform control.
2Device complexity
If DC current is used for OLED operation, then the driving scheme is simple, but image sticking effects occur due to non-uniform recombination rate profile
Solution Approach 1:
The patent implements periodic action by using pulsed current waveforms to drive the OLED device. Instead of continuous DC current, the device receives periodic pulses that create time-varying recombination rates. This periodic operation allows different regions of the emissive layer to be activated in sequence, preventing the persistent non-uniform recombination patterns that cause image sticking. The periodic nature of the driving scheme maintains simplicity while effectively eliminating the harmful image sticking effect.
3Reliability
If pulsed driving schemes are implemented to extend OLED lifetime, then device lifetime is extended, but the driving scheme complexity increases
Solution Approach 1:
The patent applies parameter changes by systematically varying key waveform parameters including pulse width, frequency, and duty cycle. These parameter variations allow optimization of the pulsed driving scheme to extend device lifetime while managing complexity. By changing these parameters, the recombination profile can be tailored to access different zones of the emissive layer, promoting uniform aging and extending lifetime. The parameter changes provide a controlled approach to complexity, where each parameter adjustment serves a specific function in lifetime extension.
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
This approach effectively extends the operational lifetime of OLED devices by adjusting the recombination profile, reducing efficiency losses, and minimizing color alteration and image sticking issues, even when operated at low luminance ranges.
Implementation Method 1
OLEDs make use of thin organic films that emit light when voltage is applied across the device
Data Source
AI summary
Techniques, devices, and systems are provided that allow for driving a device such as an OLED in various pulsed modes in which a momentary luminance greater than an apparent luminance at which the OLED is to be driven is used. The use of one or more pulsed modes allows for the lifetime of the OLED to be extended and reduces image sticking. Pulsed modes are also provided that allow for color tuning of the device by activating different portions of one or more emissive areas of the device.