A series of blue-emitting poly(2

7-carbazole)s substituted with N-phenylcarbazole (BCzPCz01-BCzPCz10) have been synthesized via Suzuki polymerization.By reducing the loading of Pd catalyst from 10 to 1

their number-average molecular weights are correspondingly increased from 27000 to 69000 while their polydispersity indexes (PDI) remain in the range of 2.5 to 3.0.And the effect of the molecular weight on their photophysical

electrochemical and device properties is then thoroughly investigated for these obtained polymers.Most importantly

the introduction of rigid N-phenylcarbazole can effectively tune the interchain interactions

and improve the color purity of blue emission.As a result

all the polymers show film photoluminescent quantum yields as high as 0.40 and excellent spectral stability

for no green emission often appeared in polyfluorenes is observed here under annealing or electric field conditions.Single layer polymer light-emitting diodes are fabricated with a configuration of indium tin oxide (ITO)/poly(3

4-ethylenedioxythiophene):poly(styrene sulfonic acid) (PEDOT:PSS)/polymer/Ca/Al.Among these polymers

BCzPCz01 exhibits a peak luminous efficiency of 0.33 cd/A with Commission Internationale de L'Eclairage (CIE) coordinates of (0.18

0.12).The device performance is improved by about 65% in comparison to that of poly(2

7-carbazole)s substituted with triphenylamine.These interesting results will provide a novel platform for the design of highly efficient stable blue-emitting polymers in the future.