Why is the band model not contradictory to molecular theory in organic electroluminescence?

Xu, Zheng; Qu, Chong; Teng, Feng; Zhang, Fujun; Meng, Lijian; Xu, Xurong
February 2005
Applied Physics Letters;2/7/2005, Vol. 86 Issue 6, p061911
Academic Journal
In organic electroluminescence there is a sharp contradiction between the applicability of band model and molecular theory. This contradiction arose from the very beginning of extended study. In this report we studied the blue spectral shift in the newly discovered solid state cathodoluminescence when the applied voltage is increased. There are three different kinds of spectra in three intervals of applied voltage. The reason of this spectral shift is found to be the field ionization of exciton. The switching on of recombination starts only after the beginning of this field ionization. The exciton emission obeys molecular theory and the recombination obeys band model. Thus the demarcation is the appearance of field ionization of excitons. Since the ionization changes with electric field continuously, there is a region of coexistence of these two processes.


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