Bovero Enrico, Van Veggel Frank C J M
Department of Chemistry, University of Victoria, P.O. Box 3065, Victoria BC, Canada, V8W3V6.
J Am Chem Soc. 2008 Nov 19;130(46):15374-80. doi: 10.1021/ja803477h. Epub 2008 Oct 22.
Currently, photonic crystals are attracting a lot of interest because of their ability to harvest light from a device into specific directions and wavelengths. In this work we have proven the theoretical prediction that in the case of an emission overlapping with the photonic stop band, the intensity is redistributed at different wavelengths. This prediction has two major consequences: (i) the total QY remains the same and (ii) the intensity increases just outside the band gap. In our case, Eu(2+) is the responsible emitter in a hybrid material based on GaN on silica, which has a fairly broad emission with its maximum at 500 nm. The GaN and Eu(2+) were placed inside an inverse opal of silica (air voids in silica matrix). The size of the holes in the different samples was varied between 300 and 600 nm, in order to tune the stop band in different positions with respect to the Eu(2+) emission. The measured quantum yield was constant for the different samples at about 5%, the lifetime of the Eu(2+) increased in the forbidden range, and its emission intensity was squeezed toward the side of the stop band, with a concomitant decrease of the lifetime. The enhancement of the emission intensity at a certain energy range opens new possibilities for the design of more efficient devices, providing color purification and intensification at whichever wavelength is needed.
目前，光子晶体因其能够将器件发出的光收集到特定方向和波长而备受关注。在这项工作中，我们证实了理论预测，即在发射与光子禁带重叠的情况下，强度会在不同波长处重新分布。这一预测有两个主要结果：（i）总量子产率保持不变；（ii）在带隙之外强度增加。在我们的案例中，Eu(2+)是基于二氧化硅上的氮化镓的混合材料中的发光体，其发射光谱相当宽，峰值在500nm处。氮化镓和Eu(2+)被置于二氧化硅反蛋白石（二氧化硅基质中的空气空隙）内部。不同样品中孔的尺寸在300至600nm之间变化，以便将禁带调至相对于Eu(2+)发射的不同位置。不同样品测得的量子产率恒定在约5%，Eu(2+)的寿命在禁带范围内增加，其发射强度向禁带一侧压缩，同时寿命降低。在特定能量范围内发射强度的增强为设计更高效的器件开辟了新的可能性，可在任何所需波长处实现颜色纯化和增强。
