Design of organic light-emitting display and organic solid-state lighting with high-efficiency-enhancement patterned microlens-array film
Date Issued
2010
Date
2010
Author(s)
Chen, Kuan-Yu
Abstract
Organic displays have been recently considered as the first choice of the hand-held devices, e.g., PDA mobile phones and digital cameras, due to the advantages of wide viewing angle and high color gamut. Besides, because of the capabilities of large-area roll-to-roll flexible substrate process and transparent panel, the organic solid-state lighting has been commercialized. However, the planar OLED has the low out-coupling efficiency around 20%. We set up a precise experimentally verified optical model of OLEDs. Then we apply this model to design the center-hollowed MAFs (microlens-array films) to solve the dilemma of efficiency enhancement and image quality. Besides, with the pixel-partition scheme and auxiliary electrodes, the large-area OLEDs have higher angular luminance and better electrical conduction.
Traditionally, there has been a dilemma between high efficiency enhancement (by attaching the MAFs of higher fill factor and larger height ratio) and high image quality (low blur-width and high universal image quality index) by the regular of fully-filled MAFs. However, our unique center-hollowed MAF design is a win-win solution to this dilemma.
The micro-structured substrate cannot be calculated by the thin-film optics and the optical interference effect by the thickness variation of organic layers also cannot be distinguished by the ray-tracing approach. However, combining the electromagnetic theory and Monte Carlo based geometrical optical ray-tracing approach, we establish the experimentally validated optical model to precisely predict the angular luminance enhancement ratios of various organic layer thickness and parameters of the MAFs. Besides, the absolute value of light-extraction efficiency among various thicknesses of organic layers can also be acquired by the mode analyses.
Auxiliary electrodes are often used in the large-area OLED panels for better electrical conduction along the emissive area. However, the auxiliary electrodes often block some portions of light. Thus, we propose the center-hollowed MAFs attachment to recover the optical loss by the absorption of auxiliary electrodes. For example, for a 15 × 15 cm2 organic lighting panel, the pixel-partition scheme assisted with auxiliary electrodes can eliminate the voltage drop from the electrode to the center of the diagonal of the active area by more than 20 V; the pixel-partition scheme assisted with center-hollowed MAFs can lead luminance enhancement at normal direction by 104% and 127% with high-refractive-index substrate which is more than two times that of the reference single un-partitioned large-area pixel.
Subjects
optical simulation
microlens-array films (MAFs)
light-extraction efficiency enhancement
organic light-emitting displays
image quality
organic solid-state lighting
and auxiliary electrodes
Type
thesis
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