A series of novel carbazole/aminoalkyl-substituted fluorene based main chain copolymers (poly［3

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

9-bis(3′-(N

N-dimethylamino)propyl)-2

7-fluorene)-4

7-(2

1

3-benzoselenadiazole)］(PCzN-BSeD)) with different contents of 2

1

3-benzoselenadiazole (BSeD) were synthesized by Suzuki coupling reaction.Through a postpolymerization treatment on the terminal amino groups

corresponding quaternized ammonium polyelectrolyte derivatives (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-benzoselenadiazole)］ dibromide (PCzNBr-BSeD)) were obtained. It was observed that the efficient energy transfer occured under optical and electrical excitation on the narrow band gap BSeD site for both the neutral and the quaternized copolymers.Devices with poly(3

4-ethylenedioxythiophene)/poly(vinylcarbazole) (PEDOT/PVK) as an anode buffer

the external quantum efficiencies of the copolymer show similar devices performance to those by using poly(3

4-ethylenedioxythiophene) (PEDOT) only.It indicated that introduction of a carbazole segment into polymer main chains offered the enhanced hole-injection and transport properties.It was also found that devices from these polymers with a high work-function metal cathode such as Al showed similar devices performance to that by using the low work-function cathode such as Ba

indicating the excellent electron injection ability of these polymers.