  In order to provide an accurate theoretical description of current density
voltage (J-V) characteristics of an organic heterojunction device over a wide
range of electric fields at various temperatures, it is proposed that an
accumulation of charge carriers at the heterojunction will lead to a reduction
in the barrier height across the heterojunction. Two well-known hole
transporting materials, 4,4,4-Tris(N-3-methylphenyl-N-phenyl-amino)
triphenylamine (MTDATA) and
N,N-diphenyl-N,N-bis(1-naphthyl)(1,1-biphenyl)-4,4diamine (NPB) were used to
fabricate unipolar heterojunction devices. It is found that the J-V
characteristics depends strongly on applied bias. The simulated J-V
characteristics of the heterojunction device, with the modified injection
model, are found to be in excellent agreement with the experimental data.
