Electrical conductivity of 1,3-bis(N-carbazolyl)benzene (mCP) on a hole-transport bilayer

Abstract

We studied the electrical conductivity of a bilayer specimen of N,N′-bis(naphthalen-1-yl)-N,N′-bis(phenyl)benzidine (α-NPD) and 1,3-bis(N-carbazolyl) benzene (mCP). The conductivity of indium tin oxide ITO/(heptadecafluoro-1,1,2,2-tetrahydrodecyl)triethoxysilane (FSAM)/α-NPD(50 nm)/Al can be explained by the space-charge-limited current (SCLC) model. In an α-NPD(50 nm)/mCP(10 nm) specimen, the current is similar to that in an α-NPD(50 nm) specimen despite the existence of a hole barrier between the α-NPD and mCP. The current in an α-NPD/mCP specimen is also proportional to the square of the voltage. We propose a conduction model that combines SCLC in the α-NPD layer and tunneling in the mCP layer.