industry LEDs
The wavelength range, in terms of the dominant wavelength, is currently 590 nm to 645 nm, and 560 nm and 570 nm LEDs will follow in the latter part of 2012.
Commercial opportunities An already-widespread application is the combination of a highly efficient – but aesthetically unpleasant – cold- white LED with amber or red one, because this lowers the colour temperature to a more visually pleasant and high-quality white. This modification is something of a win-win, because it increases the overall efficiency and the colour-rendering index.
Our breakthrough in red LED efficiency will also aid projection and signalling applications, which value a highly efficient red source. Mobile applications are also set to benefit, with customers enjoying brighter screens, or benefitting from longer battery life. While in industry, lower energy consumption will trim operating expense, and brighter devices will cut the cost of initial installation.
One area where highly efficient LEDs seem assured to make a positive impact is in LED-illuminated green houses. Thanks to incredibly high efficiencies, energy
costs can plummet by almost a factor of two compared with conventional lighting; and on top of this, LED- cooling is made easier. For example, our state-of-the-art LEDs can generate 75 percent more light at a given electrical power than a source with 40 percent peak efficiency. And if waste heat is the chief concern, our LEDs can generate two-and-a-half times as much light compared with the present lighting fixtures.
What next?
Wringing out further improvements in efficiency is increasingly challenging as the devices creep towards the ideal goal of 100 percent. Efforts will undoubtedly continue in this direction, nudging efficiency from 60 to 70 percent, but this will be carried out in conjunction with programmes to improve production and processes.
There is also a need to improve LED performance at high currents and temperatures. Characterizing devices at room temperature is common practice, even though many devices actually operate in far hotter environments, such as 100°C. To address this, we are working to optimise output power at this temperature, as well as reducing the shift in operating parameters with temperature.
Another challenging area, where issues continue to evolve, relates to optimisation of the coupling of light out of the LED. Research is ongoing to extract every generated photon, at both the package and the die level. New die configurations promise to deliver significant progress in this direction.
As we continue to develop and improve our long- wavelength LEDs using the approaches just outlined, our devices will be able to serve an increasing broad portfolio of applications. Further improvements are imminent, so don’t be surprised if its soon time for us to issue another ‘red alert’! A brighter future surely lies ahead for all of us.
Figure 4: Light current curve (top) and efficiency /efficacy over current (bottom) of 1mm2 laboratory package
LED in
© 2012 Angel Business Communications. Permission required.
March 2012
www.compoundsemiconductor.net 25
Figure 5: Light output and wall plug efficiency over operating current for a Osram’s 1mm2 die emitting at a peak wavelength of 660 nm
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88 |
Page 89 |
Page 90 |
Page 91 |
Page 92 |
Page 93 |
Page 94 |
Page 95 |
Page 96 |
Page 97 |
Page 98 |
Page 99 |
Page 100 |
Page 101 |
Page 102 |
Page 103 |
Page 104 |
Page 105 |
Page 106 |
Page 107 |
Page 108 |
Page 109 |
Page 110 |
Page 111 |
Page 112 |
Page 113 |
Page 114 |
Page 115 |
Page 116 |
Page 117 |
Page 118 |
Page 119 |
Page 120 |
Page 121 |
Page 122 |
Page 123 |
Page 124 |
Page 125 |
Page 126 |
Page 127 |
Page 128 |
Page 129 |
Page 130 |
Page 131 |
Page 132 |
Page 133 |
Page 134 |
Page 135 |
Page 136