ACEL characteristics of metal Er and ErF

3

doped thin films with different doping concentration have been studied. The relation of ACEL brightness with doping concentration shows that for ACEL the optimum doping concentration of ZnS:ErF

3

thin film is 5×10

3

g/g. It is lower than that of ZnS:Er

3+

thin film (1×10

-2

g/g). The emission spectra of the two samples are obviously different. At nearly the same concentration

the red emission peak is stron-ger in ZnS:ErF

3

than in ZnS:ErF

3

thin film. The decay of excited state

2

H

11/2

is also different in two samples. At lower concentration (-10

-3

g/g)

the decay of excited state

2

H

11/2

in ZnS:Er

3+

thin film obeys single exponential form

but the decay of excited state

2

H

11/2

in ZnS:ErF

3

thin film consists of two componentry-fast and "slow exponential "forms. We have studied the relation of latio of green emission peak to red one with applied voltage. This ratio increases with the applied voltage in" ZnS:Er

3+

thin film when the concentration is low (-10

-3

g/g)

but remains unchanged in ZnS:ErF

3

thin film. At higher concentration (~10

-2

g/g) this ratio decrease with applied voltage in ZnS:ErF

3

thin film. Therefore

the interaction between RE ions

the cross relaxation

becomes important when the concentration gets higher. This process is affected by surroundings of RE ions. The excistence of F

-

ion enhances the cross relaxation process and it is the main reason why ZnS:ErF

3

thin film has lower optimum concentration for ACEL. Although ErF

3

"lumocen" has large impact cross section but the optimum concentration is lower. To obtain higher green ACEL thin film

ZnS:Er

3+

is better than ZnS:ErF

3

.