Inclined Electrode Structure for OLED Light Extraction
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Solution Overview
Problem
Conventional self-luminous light-emitting devices face challenges in light extraction efficiency due to total reflection at the interface between the light-emitting layer and the upper electrode, leading to inefficient light extraction and increased drive voltage, especially when the bank opening size is large or small.
Innovation Solution
A light-emitting device with a bank having an inclined through-hole, where the lower electrode forms a reflective layer on the inclined sidewall, allowing light to be extracted externally and functioning as an electrode, thereby increasing the light-emitting area and suppressing drive voltage rise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a reflective layer is formed on the inclined face of the bank by covering the lower electrode layer with an insulating film, then light extraction efficiency is improved, but the electrode area is reduced and drive voltage rises
Solution Approach 1:
The patent applies local quality by differentiating the treatment of different bank surfaces: the inclined face receives the insulating film for light extraction, while the top surface and inner sidewall remain exposed to maintain electrode functionality. This selective application allows simultaneous optimization of optical performance and electrical performance in different locations.
Solution Approach 2:
Instead of making the entire lower electrode non-functional by covering it completely, the patent inverts the approach by leaving critical electrode areas exposed while only covering the inclined face. This partial exposure strategy reverses the conventional thinking of complete coverage and maintains both reflective function and electrode function.
2Ease of manufacture
If the bank opening size is made large, then the manufacturing process is simplified, but light extraction efficiency deteriorates due to increased total reflection
Solution Approach 1:
The patent changes the geometric parameter of the bank from a conventional vertical cylinder to an inclined structure with specific angle ranges (30-60 degrees). This parameter change modifies the light propagation path and reduces total reflection, enabling efficient light extraction even with larger opening sizes that are easier to manufacture.
Solution Approach 2:
The patent introduces a new dimensional aspect by tilting the bank structure sideways rather than maintaining vertical symmetry. This dimensional change creates an inclined face that redirects light at angles favorable for extraction, adding a new degree of freedom to the light management strategy.
3Loss of energy
If the bank opening size is made small, then light extraction efficiency is improved, but drive voltage rises due to reduced electrode area
Solution Approach 1:
The patent applies local quality by preserving the electrode function on the top surface and inner sidewall of the bank while only modifying the inclined outer face for optical purposes. This localized differentiation allows small opening sizes to maintain sufficient electrode area for low drive voltage while achieving high light extraction efficiency through the inclined reflective face.
4Loss of energy
If an insulating film is formed to create a reflective layer, then light extraction is improved, but the lower electrode layer loses its electrode function on the covered areas
Solution Approach 1:
The patent applies local quality by selectively forming the insulating film only on the inclined face where light extraction is needed, while leaving the top surface and inner sidewall exposed to maintain electrode functionality. This spatial differentiation ensures that optical enhancement and electrical functionality are achieved in their respective optimal locations without mutual interference.
Solution Approach 2:
The patent segments the bank surface into functionally distinct zones: the inclined face for optical reflection and the top/inner surfaces for electrical conduction. This segmentation allows each zone to be optimized independently for its specific function, with the insulating film applied only to the reflective zone.
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 enhances light extraction efficiency and prevents a rise in drive voltage by reflecting and emitting light from the inclined electrode surface, effectively utilizing the bank sidewall as a light-emitting area.
Implementation Method 1
light emission occurs in a thin light-emitting layer interior, making total reflection likely to occur at an interface between the above-described compound layer electrode, including the light-emitting layer, and the upper layer electrode
Data Source
AI summary
A light-emitting device includes a bank provided with an opening including an opening sidewall that is inclined, a lower layer electrode provided with an inclined face and formed on the bank, closing the opening, a upper layer electrode provided with an inclined face and formed above the second electrode, and an EL layer provided with an inclined face and formed between the lower layer electrode and the upper layer electrode, adjacently to the lower layer electrode and the upper layer electrode. The light-emitting device further includes a first refractive index layer having a refractive index higher than 1.7, and a second refractive index layer having a refractive index lower than the refractive index of the first refractive index layer. The first and second refractive index layers are formed in this order on the upper layer electrode at a through-hole.