n-Type
doping with (4-(1,3-dimethyl-2,3-dihydro-1H-benzoimidazol-2-yl)phenyl)
dimethylamine (N-DMBI) reduces a work function (WF) of graphene by
∼0.45 eV without significant reduction of optical transmittance.
Solution process of N-DMBI on graphene provides effective n-type doping
effect and air-stability at the same time. Although neutral N-DMBI
act as an electron receptor leaving the graphene p-doped, radical
N-DMBI acts as an electron donator leaving the graphene n-doped, which
is demonstrated by density functional theory. We also verify the suitability
of N-DMBI-doped n-type graphene for use as a cathode in inverted polymer
light-emitting diodes (PLEDs) by using various analytical methods.
Inverted PLEDs using a graphene cathode doped with N-DMBI radical
showed dramatically improved device efficiency (∼13.8 cd/A)
than did inverted PLEDs with pristine graphene (∼2.74 cd/A).
N-DMBI-doped graphene can provide a practical way to produce graphene
cathodes with low WF in various organic optoelectronics
