In this paper

the relations and differences between DCEL and ACEL characteristics of powder ZnS:Mn

Cu DCEL devices

and their mechanism are investigated.Experiments show that the impedance characteristics both under DC and AC voltage operations are not consistent and related.But the exciting current

I

A

and the brightness

B

A

under AC voltage

and the brightness

B

D

and the efficiency η

D

under DC voltage tend to consistency to certain extent.The efficiency η

A

under AC voltage is contrary to above four parameters.DCEL devices are strongly non-linear and non-symmetrical in photoelectric characteristics.In positive half-cycle of AC voltage(or under DC voltage)

DCEL devices are excited by high electric field and low current.Under this circumstance

the luminance is dominared by electric field.On the contrarily

in negative half-cycle of AC voltage DCEL devices are operated by low electric field and large current.At this case

the luminance is dominated by current

no;by field.Under AC voltage

the luminance of DCEL devices may show characteristics of positive or negative half-cycle

or complex characteristics of both positive and negative half-cycle

depending on the phosphors

the art of devices

the forming process and operation voltage.The above point of view can explain all of the experimental results mentioned in.this paper.