Abstract The current–voltage–temperature (I–V–T) characteristics of Al/NPB/p-Si Schottky diodes were discussed in detail in this paper. It shows an abnormal decrease of the Schottky barrier height and increase of ideality factor as the decrease of measured temperature. The series resistance was evaluated and it is found that the series resistance increases as the increase of the measurement temperature. The Gauss distribution of the inhomogeneous of the barrier was brought to discuss the contact interface. The characteristics have been interpreted based on the thermionic emission (TE) mechanism with Gaussian distribution of the barrier heights of ϕ¯b0 is 0.96eV and standard deviation σso is equal to 0.13V. In addition, the ln(I0/T2) vs. 1/T plot yields the effective Richardson constant of 1.47×10−2Acm−2K−2 for the Al/NPB/Si diode which is lower than the known value of 32Acm−2K−2 for Si. This deviation is attributed to the inhomogeneous barrier heights and potential fluctuations at the contact interface that consists of low and high barrier areas. The modified Richardson plot shows a straight line relationship between ln(Js/T2)-(q2σso2/2k2T2) vs. 1000/T, and gives a value of A∗=30.1Acm−2K−2.