With their ionic side groups being attached to the conjugated main chain

conjugated polyelec-(trolytes)(CPs) can offer particular properties compared with the normal "neutral" polymers

having attracted considerable attention in recent years.Generally speaking

there are only a few reports on electroluminescent properties of LEDs fabricated from CPs.Previously

our group has reported the first LEDs based on ammonium functioned polyfluorene electrolytes

and a series of high-efficiency

environment-friendly electroluminescent polymers.With their terminal amino groups and quaternized ammonium groups

the devices from such polymers show the excellent electron injection ability.As a good performance of a device requires the balance between the hole and electron transporting in the emissive layer

it can feasible to synthesize polymers containing hole-transporting units on the basis of our previous work.It is well-known that carbazole-containing polymers are good hole-transporting materials due to the electron-donating capabilities associated with the nitrogen in the carbazole.A series of novel aminoalkyl-substituted fluorene/carbazole based main chain copolymers with benzothiadiazole(BTDZ) of different content were synthesized by Suzuki coupling reaction: poly[3

6-(N-(2-ethyl-(hexyl))carbazole)-(9

9-bis(3′-(N

N-dimethylamino)propyl)-2

7-fluorene)-4

7-(2

1

3-benzothiadiazole)](PCzN-BTDZ).Through a postpolymerization treatment on the terminal amino groups

their quater-(nized) ammonium polyelectrolyte derivatives were obtained: poly[3

6-(N-(2-ethylhexyl)carbazole)-(9

9-bis(3′-((N

N-dimethyl)-N-ethylammonium)propyl)-2

7-fluorene)-4

7-(2

1

3-benzothiadiazole)] dibromide(PCzN-BTDZBr).It was found that devices from such polymers with the high work-function metal(cathode) such as Al show similar device performance to that by using the low work-function cathode such as Ba

indicating the excellent electron injection ability of these polymers.And it was observed that the efficient(energy) transfer occurs by exciton trapping on the narrow band gap BTDZ site for both the neutral and the(quaternized) copolymers.The addition of BTDZ comonomer also improves their PLED devices performance.When PEDDT/PVK was used as an anode buffer

the external quantum efficiency of the copolymer PCzN-BTDZ1 is 0.99%

which is higher than that of the copolymer PCzN in the same device configuration.