Quantum dots are increasingly used in displays to achieve high color gamut at high efficiency. This paper describes the impact of quantum dot lifetime on long-term display performance and the methods used for predicting in-device lifetime from accelerated aging results. Test methods are described which give confidence in aging predictions. Author KeywordsQuantum Dot; LCD; QD; Quantum Dot Enhancement Film; QD lifetime; QD reliability; wide color gamut. Objective and BackgroundQuantum dots (QDs) that are implemented in Liquid Crystal Display (LCD) backlights convert a portion of the high energy blue light from a light emitting diode (LED) source to lower energy red and green light. QD emission wavelength is dependent upon the size of the QD. Because the sizes of QDs can be controlled very precisely and their emission is spectrally narrow, this enables displays with high color gamuts [1] [2] [3]. The relative mix of red and green QDs combined with their location in the backlight determine the display white point. As with LEDs, QDs have a finite lifetime and eventually stop emitting light. In the LCD application, this results in a reduction in luminance and can also result in a change in color if the relative lifetimes between the QDs and LEDs differ significantly.Ultimately, an LCD must maintain a front-of-screen luminance and color specification for the lifetime of the display under normal operating conditions. For televisions, manufacturers typically like to specify lifetimes of 20,000 to 30,000 hours. This represents approximately 2.25 to 3.5 years of continuous operation at so-called "1x" conditions. Testing at these conditions is impractical, so accelerated test methods must be developed, and the results must be translated into "1x" conditions. This paper explains the testing and models used to determine the lifetime of QDs in film for use in LCDs.Two factors dominate the lifetime of the QD based film: temperature and radiant flux.It can be shown that the temperature largely follows an Arrhenius relationship within a reasonable range. The more challenging acceleration component is the acceleration due to flux. Although it may be simplest to think of the amount of incident blue flux when determining the lifetime of the QD-film, this poses many challenges. These challenges are related to the recycling of the backlight unit and the optical path that the blue flux takes. Without fully characterizing these in the accelerated systems and the in-device system a good relationship cannot be established for the blue flux. We have found, both conceptually and practically, it is simpler to think of the amount of converted flux when determining the flux acceleration. This is because the amount of red and green light generated by the QD-film is a direct reflection of the amount of transitions the QDs are undertaking, or put another a way, the amount of work they are performing.Using this understanding we have developed measurement techniques that allow us to directly measure and then estimate the length of time our Q...
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