In this paper

the distribution and the origin of the luminescence region in DCEL panels (sandwich cells) have been investigated. The experiments are carried out by observing the cross-section of the panels in microscopy. It is found that the luminescence region in DCEL devices (sandwich cell) can be located anywhere

for example

at the region close to anode or cathode

or in the middle of phosphor/binder layer. It is suggested that the distribution of luminescence region of DCEL panels is random.The position of luminescence region depends mainly on the way of forming process and is also related to the structure defects in the phosphor/binder layer

the properties of phosphor and the electrode materials etc.