Abstract
Optical performance in terms of light efficiency, color crosstalk and ambient contrast ratio were analyzed for blue GaN-based micro-light emitting diodes (micro-LEDs) combined with red/green quantum dots (QDs)-polymethyl methacrylate (PMMA) films. The thickness and mass ratio of QDs films are two critical factors in affecting the performance of micro-LEDs. Firstly, the precise optical modeling of QDs-PMMA films is established based on the double integrating sphere (DIS) testing system and inverse adding doubling algorithm (IADA) theory. Red and green QDs-PMMA films are composed of ZnCdSe/ZnS QDs and green ZnCdSeS/ZnS QDs, respectively. The fundamental optical parameters of QDs-PMMA films, including scattering, absorption and anisotropy coefficients, are obtained successfully. Secondly, based on these optical parameters, the Monte Carlo ray tracing method is applied to analyze the effect of a QDs-PMMA film’s thickness and mass ratio on the optical performance of micro-LEDs. Results reveal that the light efficiency first increases and then decreases with the increase of a QDs film’s thickness or mass ratio, owing to the scattering characteristics of QDs. Different from the variation tendencies of light efficiency, the crosstalk between adjacent pixels increases as the QDs-PMMA film’s thickness or mass ratio increases, and the ambient contrast ratio is kept stable when the thickness increases. The mass ratio variation of QDs film can change the optical performance of micro-LEDs more effectively than thickness, which demonstrates that mass ratio is a more important factor affecting the optical performance of micro-LEDs.
Highlights
Owing to their advantages of low power consumption, long life, high brightness and excellent reliability, light-emitting diodes (LEDs) have been developed rapidly for many years [1,2,3]
It has recently been discovered that colloidal quantum dots (QDs) as a novel light conversion material can solve the above issue [8], and the micro-LED display combined with a QD has the properties of high resolution, a wide color gamut and a superior color rendering index
The mass ratio (MR) of QDs to polymethyl methacrylate (PMMA) will be used as an solution is introduced into a customized mold, which is placed on a horizontal platform, and the important factor to evaluate the effect of QDs on the optical performance of micro-LEDs in later red/green QDs films are obtained after toluene volatilizing
Summary
Owing to their advantages of low power consumption, long life, high brightness and excellent reliability, light-emitting diodes (LEDs) have been developed rapidly for many years [1,2,3]. For realizing the full color display of micro-LEDs, different technologies have been presented, such as combining the three colorized red, green and blue (RGB). The blue micro-LED chip is used to excite light conversion material to generate full color, which is a preferable method. The phosphor cannot be uniformly coated on a micro-LED due to its large size (>10 μm), leading to an uneven color distribution and a low light conversion efficiency. It has recently been discovered that colloidal quantum dots (QDs) as a novel light conversion material can solve the above issue [8], and the micro-LED display combined with a QD has the properties of high resolution, a wide color gamut and a superior color rendering index. Optical performance, including light efficiency, color crosstalk and ambient contrast ratio for GaN-based micro-LEDs combined with a QDs film are obtained through this simulation. The simulation result is analyzed, and the optimal parameters of the QDs film will be obtained
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