发光寿命在发光特性表征中的重要影响

Important Influence of Lifetime in Characterizing Luminescence Traits

吸收是发光的前提条件,吸收变了,发光的其他特性也就随之而变。但是发光寿命的长短又会反过来影响吸收的多少, 这不仅存在于光致发光中, 而且是一个普遍规律。从电场引起的场致发光中发现,在同一种材料中掺入两种发光寿命长短相差悬殊的发光中心Cu和Mn,利用激发电源频率的变化,明确地显示出发光寿命短的Cu的发光与发光寿命长的Mn的发光强度之比随频率的增加而增大,而且也显示了Cu的两种发光也有这种规律。实验结果说明,这种规律只取决于发光中心的寿命长短,而与激发方式及猝灭原因无关。

Absorption is the underlying reason for the change of luminescence traits. And the lifetime influences on the absorption in turn. That is a common law, it is not only suitable for photoluminescence, but also other types of luminescence. In field of electroluminescence, there are two kinds of luminescence center blue have dramatically dissimilar lifetime, in the co-doped ZnS∶Cu, Mn material. The experiment clearly demonstrates that the ratio of luminance of Cu and Mn change with the driving frequency. This law is also fit for the change of luminance in Cu, which has blue and green luminescent centers. The experiment proves that this law has something to do with lifetime and nothing to do with the way of exciting and the reasons is abruptly quenching. No matter what quenching is, the lifetime of centers must be shortened, for shorter lifetimes centers the inten- sity increases with the increase of driving frequency more quickly. The luminescence of singlet and triplet states in organic electroluminescence is crucial in determining the overall efficiencies. The density of states in singlet and triplet levels is 1∶3. The transition from triplet state to singlet state is generally forbidden. People considered that the luminescence efficiency is limited to 1/4. But they ignored that their lifetimes are quite different, and this situation influences on the efficiency of luminescence. So the efficiency of luminescence in organic electroluminescence may be greater than 25%. The experiment also demonstrates the correctness of relationship between the differential cross-section and lifetime which was brought forward in thin film electroluminescence. In the case of thin film electroluminescence the differential cross-section of excitation is inversely proportional to the lifetime center. This result provides the basis of fabricating color tunable display panel using a single phosphor material. The rate of absorption of luminescent materials is controllable by luminescence lifetime, and the effect influences on the brightness and apparent efficiency of luminescence.