Gu et al. Nanoscale Research Letters 2011, 6:199 http://www.nanoscalereslett.com/content/6/1/199 Page 8 of 12 Figure 9 LED-based and LED-plus-phosphor-based approaches for white light sources implemented as di-, tri-, and tetrachromatic sources. The trichromatic approaches can provide a reasonable trade-off between color and luminous source efficiency. Reproduced from [72]. Copyright the American Association for the Advancement of Science, 2005. blue light leads to white light emission. Instead of enhancing the IQE or LEE of the device, this configura- tion enhances light absorption by the CdSe/ZnS QWs via coupling between the QWs and LSP generated by the Au NPs. Spectral tunability, high quantum effi- ciency, and photo-stability are the advantages of this method. Another possible but seldom reported method to increase the efficiency of white light emitters is to incorporate NPs of different geometries in a device. As demonstrated in microwave frequencies, combination of NPs with various geometries results in several transmis- sion dips corresponding to the type of NPs [74]. Hence, if different NPs with properly designed geometries are introduced into a white light emitter, the various light components can be enhanced selectively, thereby produ- cing light emitters giving the desirable spectrum. Flat panel displays Commercial flat panel displays are typically liquid crystal [LCD] and plasma displays [PD]. Although these two schemes dominate the market today, many problems still remain unsolved, for instance, narrow viewing angle in spite of big improvement since its inception, poor resistance to shock associated with LCDs, complexity in small-area fabrication and UV radiation inherent to PDs. Consequently, scientists continue to search for other display schemes and devices. LED is a viable alter- native due to the high intensity and energy saving. Unlike LCDs, commercial LED displays usually adopt organic emitting materials, and an image of which is shown in Figure 10 [75]. OLEDs have attracted Figure 10 Image of an organic display panel developed by Philips Electronics. Reproduced from [75]. Copyright Nature Publishing Group, 2004.