Tapered Quantum Dot Containers for Micro-LED Light Coupling
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Solution Overview
Problem
Existing micro-LED displays face challenges in efficiently collecting and directing light from micro-LEDs, especially when using quantum dot color conversion materials, due to the broad angular distribution of light, which can result in wasted light outside the acceptance cone of the system.
Innovation Solution
The use of axially symmetric QD containers with varying cross-sectional areas, such as single taper and double taper (hourglass) designs, to optimize the coupling of light from micro-LEDs into the acceptance cone of the system, thereby enhancing light collection and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If quantum dot color conversion materials are used in micro-LED displays, then color conversion is achieved, but light is wasted outside the acceptance cone due to broad angular distribution
Solution Approach 1:
The quantum dot container is divided into multiple segments including a base portion, a sidewall portion, and an optional apex portion. Each segment serves a specific function: the base portion collects light from the micro-LED, the sidewall portion redirects light at specific angles, and the apex portion focuses light into the acceptance cone, thereby reducing light loss while maintaining color conversion efficiency
Solution Approach 2:
The patent introduces angular dimension control through specifically designed sidewall angles (e.g., 45 degrees) and apex angles to redirect light from broad angular distribution into the acceptance cone. This dimensional control of light propagation angles transforms the light collection problem from a three-dimensional broad distribution into a focused directional beam within the acceptance cone
2Productivity
If tapered QD container geometries are used to optimize light coupling, then light collection efficiency is improved, but device complexity increases
Solution Approach 1:
Different portions of the quantum dot container are assigned different geometric properties: the base portion has a larger cross-sectional area to capture broad angular light, the sidewall portion has specific taper angles (e.g., 45 degrees) to redirect light, and the apex portion has a smaller cross-sectional area to focus light into the acceptance cone. This local differentiation of geometric properties optimizes light coupling at each stage while maintaining overall system feasibility
Solution Approach 2:
The patent employs curved and tapered geometries including conical apex portions and rounded transitions between segments. These curved surfaces smoothly redirect light rays through controlled refraction and reflection, improving light coupling efficiency while avoiding sharp edges that would cause light scattering and manufacturing difficulties
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
These tapered QD container geometries improve the overall efficiency of micro-LED displays by increasing light coupling into the acceptance cone, leading to better performance and potentially longer battery life in wearable displays.
Implementation Method 1
Light emitted by micro-LEDs, and especially light subsequently converted to another color (e.g. in a quantum dot color converter)
Data Source
AI summary
A color micro-LED display chip includes light-emitting diodes (LEDs) and quantum dot (QD) containers that contain quantum dots. The QD containers are positioned to receive light emitted from the LEDs. The QD containers are shaped to have an entrance face, an opposing exit face and a waist located between the two faces. The waist has an area that is less than an area of one of the faces and less than or equal to an area of the other face.