Gu et al. Nanoscale Research Letters 2011, 6:199 http://www.nanoscalereslett.com/content/6/1/199 Page 3 of 12 Emitting materials and configurations InGaN/GaN multiple QW Alq3 thin film InGaN/GaN QW InGaN/GaN QW Organic poly Si QD ZnMgO alloys ZnO film Si-on-insulator CdSe/ZnS nanocrystals Si QD GaN Figure 2 Noble metallic NP layer deposited on or within a conventional LED to enhance efficiency of device. This new class of LEDs can be used in various compelling applications. spontaneous emission rate of the light emitters can be improved in the presence of silver SPPs since the enhanced local electric field at the LSPR frequency plays a similar role as the evanescent wave induced by SPPs [31,32]. An example of the IQE enhancement in LSPR- enhanced LEDs is the GaN-based LED developed by Kown et al. [33]. The optical output power increases by 32.2% at an input current of 100 mA, and the time- resolved PL measurement shows that the PL decay time in the presence of Ag NPs is significantly reduced. As a result, the spontaneous emission rate and the IQE are better. Table 1 Summary of representative experimental results showing the important relationship between the LSPR energy and emission energy in order to attain the best enhancement Peak emission energy (nm) Metal used Optical properties of metal layer Enhancement References 463 525 550 465 575 600 357 380 1,140 580 775 440 Ag Au Ag Au Ag Ag Pt Ag Ag Au Ag Ag Transmittance exhibits absorption from 396 to 455 nm A peak in absorption at 510 nm A dip in transmission at about 550 nm A dip in transmission in 511 nm Large absorption from 330 to 500 nm A peak in absorption at 535 nm Extinction band near 350 nm Extinction band near 370 nm A dip in transmission at about 520 nm A peak in absorption at about 600 nm A dip in transmission at 710 nm A dip in transmission at about 440 nm 32.2% with an 100-mA Kwon et al. [33] current 20-fold Fujiki et al. [34] 150% in peak intensity with a Yeh et al. [36] 20-mA current 180% with a 20-mA current Sung et al. [37] Sixfold Qiu et al. [41] Reaches maximum at 530 nm Sixfold Threefold 2.5-fold in peak intensity 30-fold Twofold, with the peak blue shifts Twofold Kim et al. [42] You et al. [44] Cheng et al. [45] Pillai et al. [48] Pompa et al. [53] Biteen et al. [54] Mak et al. [62]