OELD is expected to become even more familiar as a flexible display and lighting panel that emits light on its own.
OELD has already taken the lead in the smartphone market, and demand is expected to grow in the tablet and laptop markets.
Therefore, it is hoped that the quality and reliability of these products will be further improved in the future.
In the evaluation of organic electroluminescence, a combination of TEM, SEM, TOF-SIMS and other methods enables structural analysis,
composition analysis, condition analysis and identification of the cause of degradation.
Cross-sectional observation of OELD
For low-density films, it is difficult to provide contrast at high acceleration voltages (several hundred kV) due to the high transmission of electrons,
but SEM-STEM images at low acceleration voltages can reflect small differences in density and provide clear compositional contrast.
It can be applied to organic EL films with small density difference, average mass difference and composition difference.
Evaluation of layer structure of OELD elements
The following are the results of cutting the OELD element in an N2 atmosphere and extracting the qualitative spectra of each layer.
By machining the OELD device in an N2 atmosphere, we were able to obtain spectra of each layer that are closer to the true state.
Depth analysis of OELD materials for RGB elements
OELD displays have the potential for high definition and low power consumption, and the market is expected to expand. In recent years,
there has been a trend toward finer arrays of pixels in order to achieve higher resolution image quality.
With the introduction of the GCIB (Ar Cluster), however, it is now possible to evaluate OELD materials with good reproducibility in the depth direction even with small pixels,
as well as degradation and diffusion evaluation of materials. 。 ※GCIB：Gas Cluster Ion Beam
A TOF-SIMS measurement was performed in a 20×100μm pixel of a commercial OELD display.
Due to the small size of the element, the conventional oblique cutting method does not show a distribution corresponding to the layer structure.
On the other hand, using GCIB, it is possible to evaluate organic materials based on the layer structure with good sensitivity.
Material structure evaluation of OELD
In order to improve the reliability of OELD, detailed structural analysis, state analysis, and identification of the cause of degradation will be even more important,as demand for OELDs expands in the future.
We will introduce examples of the evaluation of layer structures and materials using TOF-SIMS and LC/MS.
We were able to evaluate the layer structure and component information of each layer using TOF-SIMS, and analyzed the components of mass E identified by TOF-SIMS using LC/MS and a fluorescence detector to evaluate the emission wavelength and understand the component structure. Thus, a combination of TOF-SIMS and LC/MS can be used for detailed evaluation.
Evaluation of RGB elements in OELD
TOF-SIMS and SEM-STEM analyses were performed on the RGB elements of organic EL.
Both TOF-SIMS and STEM results show that the thickness of the organic film is different for each RGB element.
The depth profile results of the TOF-SIMS red element are shown below, since the thickness cannot be evaluated by TOF-SIMS.
The film thickness of the STEM result is applied to the depth.
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