Optical properties of self-assembled ZnO nanocrystals embedded in a p-phenylene biphenyltetracarboximide polyimide layer

Abstract

ZnO nanocrystals embedded in a p-phenylene biphenyltetracarboximide (BPDA-PDA) polyimide (PI) layer were formed by a thermal curing. Transmission electron microscopy and selected-area electron diffraction measurements showed that the ZnO nanocrystals were formed inside the BPDA-PDA PI layer. An absorption peak corresponding to the optical band gap of ZnO nanocrystals appeared in an ultraviolet-visible absorbance spectrum, and a transmittance spectrum showed that the average optical transmittance in the visible range was approximately 70%. A dominant band corresponding to the green emissions of the ZnO nanocrystals was clearly observed in the photoluminescence (PL) spectra. The green emission mechanism of the ZnO nanocrystals embedded in the BPDA-PDA PI layer is described on the basis of the absorbance and the temperature-dependent PL results.