Electrical characterization of ITO/CuPc/Al diodes using temperature dependent capacitance spectroscopy and I–V measurements

Sandwich structures were prepared by vacuum sublimation of 100 nm thick CuPc thin films between ITO and Al electrodes. The rectifying behavior of these devices was analyzed with dc electrical measurements as a function of temperature in the range 100–310 K. Different regimes were observed with temperature and bias dependent transition. At low bias and high temperature, the results are best explained with Poole–Frenkel type transport model, while at high bias and low temperature, space charge limited current controlled by an exponential distribution of traps dominates the transport. Electrically active defects were investigated with space charge capacitance spectroscopy, as a function of temperature and frequency. The analysis of the capacitance data shows that the CuPc layer exhibits a rather high density of localized states at Fermi level. These results are discussed and compared with those of the temperature dependent J–V measurements.