Tech Hardware Supply Chain - Gazhoo

Bhavin Shah
(852) 2800-8538
bhavin.a.shah@jpmorgan.com
Asia Pacific Equity Research
20 April 2009
Methods to generate white LED
Given the introduction of HB LED, white LEDs can be generated through different
packaging methods and allow LEDs’ entry into display backlighting and eventually
the general illumination market.
There are four methods to make white LEDs (as shown in Table 161). Blue LED
chip + yellow phosphor is the dominant method (>90%) for small-to-mid-size panel
backlights due to its low cost, while RGB LED is the more sought-after method for
large-size panel backlights due to its superior color saturation.
Table 161: Methods to generate white LED
Method Pros Cons
RGB LEDs
(red, blue, green)
Blue LED chip + yellow
phosphor
UV LED chip +
RGB phosphor
• Highest efficiency
• Tunable white point
• Widest color gamut (NTSC 104%)
• Simple
• Good color rendering
• Excellent stability and reliability
• Low cost
• RGB phosphor efficiency higher
than yellow phosphor
• Stable white point
• High color rendering
• Low voltage
ZnSe
• Single LED chip to produce white
light
• No phosphor needed
Source: Lumileds and J.P. Morgan.
• High cost
• Requires feedback control to
maintain white point
• Lower efficiency
• Narrow color gamut (NTSC 65%)
• Need patent license from
Japanese/US/EU LED players
e.g. YAG phosphor by Nichia, TAG
phosphor by Osram (85% of YAG
phosphor’s efficiency)
• Degradation due to UV package
interaction
• RGB phosphor not mature
• Need to improve UV LED chip
efficiency and reliability
• Low efficiency: 8 lm/w, 50% lower
than GaN
• Short life: 8,000 hours
Superior advantages of LED as a backlighting source: Full color saturation,
lower power consumption and thinner panels
There are numerous advantages of using RGB LEDs as the backlight source. Not
only do RGB backlights offer a significantly wider color reproduction range than
conventional CCFL backlights, they also make it much easier to reproduce colors
difficult to achieve with phosphors in CRT, PDP or surface-conduction electronemitter
display (SED) technologies. RGB LEDs make it possible to achieve color
reproduction ranges in excess of 100% of the American National Television
Standards Committee (NTSC) specifications versus CRT’s 75% and CCFL’s 72%,
and freely adjust white color expression.
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