What‘s Next for High-Power LEDs？

　　高效發光二極管是令人印象深刻的設備。許多領先的半導體公司銷售經過驗證的商業設備，功效超過100流明/瓦特，壽命超過50000小時。

　　然而，在當代的產品表現良好，氮化銦鎵（InGaN）基白光LED（最常見的類型，產生今天）有一個約250流明/ W的理論有效性限制，因此還有很大的改進余地。諸如載流子注入、內部量子和光提取效率等因素受到學術界和研究人員的密切關注，它們為領先的LED公司工作。

　　本文回顧了這些科學家和工程師迄今所取得的進展，并對我們可能看到的改進做了展望。

　　Green credentials

　　LEDs are touted as the future for environmentally-friendly lighting. Some of their green credentials come from sustainable manufacturing techniques and the use of recyclable materials， but the major benefits for the planet are in the power savings LEDs exhibit compared with traditional lighting sources.

　　Although there are several techniques for producing white light from LEDs， most contemporary commercial devices combine an InGaN LED， producing light in the blue part of the spectrum， with an yttrium aluminum garnet （YAG）-based phosphor. The phosphor absorbs some of the blue light from the LED and then re-emits it across a broad range of wavelengths comprising some green and red， and a lot of yellow. The combination of blue light from the LED and the range of colors from the phosphor appears as white to the eye （see the TechZone article “Whiter， Brighter LEDs”）。 The rest of this article will be restricted to consideration of this type of white LED.