Light-emitting device with graded band gap particles
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Solution Overview
Problem
Conventional light-emitting devices face challenges in achieving high output and high contrast while maintaining a clear boundary between light and dark regions, as they often fail to effectively control light emission from specific areas and suppress emission from other regions.
Innovation Solution
A light-emitting device configuration that includes a substrate, a light-emitting element, a light transmitting member, and a covering body with a particle group composed of titanium oxide or zinc oxide particles, where the particles near the upper surface have a narrower band gap than in other areas, allowing for controlled light absorption and scattering to achieve high contrast and output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a conventional light-emitting device structure is used, then the device can emit light, but it fails to achieve high contrast with clear boundary between light and dark regions
Solution Approach 1:
The covering body incorporates particles with spatially varying properties: particles near the upper surface have narrower band gaps than particles deeper inside. This local variation in particle properties enables selective light absorption - particles near the surface absorb stray light effectively while particles deeper inside allow transmitted light to pass through, achieving high contrast without complex structural modifications
Solution Approach 2:
The invention changes the optical parameter (band gap) of the particles based on their position within the covering body. By controlling the band gap distribution - with narrower band gaps near the upper surface and wider band gaps deeper inside - the device achieves selective light absorption and scattering that produces clear light-dark boundaries while maintaining a relatively simple overall structure
2Ease of manufacture
If the covering body uses uniform particles throughout, then manufacturing is simplified, but light absorption and scattering efficiency is reduced
Solution Approach 1:
Rather than using uniform particles throughout, the invention applies local quality by varying particle properties based on position. Particles near the upper surface have narrower band gaps for effective stray light absorption, while particles deeper inside have wider band gaps to allow transmitted light passage. This localized differentiation maintains manufacturing feasibility while significantly improving light control performance
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 device achieves high output and high contrast by selectively absorbing and scattering light, ensuring minimal light emission from regions other than the intended light extraction surface, thereby maintaining clear bright and dark areas.
Implementation Method 1
the particle group includes a plurality of titanium oxide particles or zinc oxide particles dispersed in a vicinity of the upper surface of the covering body and having a portion having a narrower band gap than that in other portions in each particle
Implementation Method 2
achieving high output and high contrast by selectively absorbing and scattering light
Data Source
Figure 1A~1B
Figure 1C~1D
Figure 2A~2C
AI summary
A light-emitting device (10) comprises: a substrate (11); a light-emitting element (12) disposed on the substrate (11); a light transmitting member (14) disposed on the light-emitting element (12); and a covering body (16) that is disposed on the substrate (11), covers a side surface of the light transmitting member (14) and/or light-emitting device (12) and has an upper surface exposed to the outside. In this device (10), the covering body (16) has a particle group composed of a plurality of particles dispersed in the covering body (16), and the particle group includes a plurality of titanium oxide particles or zinc oxide particles dispersed in the vicinity of the upper surface of the covering body (16) and having a portion having a narrower band gap than that in other portions in each particle.