Observations of Schottky and Poole-Frenkel emission in lead phthalocyanine thin films using aluminium injecting electrodes

Abstract

DC current density-voltage measurements have been performed on vacuum evaporated aluminium-lead phthalocyanine-gold sandwich structures for both electrical polarities. The electrical characteristics differed markedly depending on whether the positive hole-injectingelectrode was gold (forward-bias) or aluminium (reverse-bias). An extensive study of such characteristics revealed two distinct regions in the forward-bias characteristics. In the first of these a power-law dependence of current density (J) on voltage (V) was observed with exponent n-4, and this was identified with space-charge-limited conductivity (SCLC) controlled by an exponential distribution of trap levels of approximate concentration lO 2Sm-3 , in agreement with the authors' earlier work. In the second region a square-law dependence of J on V was observed, which was identified with SCLC controlled by traps of approximate concentration IO'6m-3 and situated at a discrete energy level. Under reverse-bias, current density was considerably lower than for forward-bias and invariably showed a linear dependence oflogJ on VII', but with different slopes in the lower and higher voltage ranges. At lower voltages this behaviour was related to Schottky emission with barrier height t/>s -I eV and width approximately 50nm, while at higher voltages Poole-Frenkel emission was identified. Measurements of capacitance C as a function of applied voltage gave a linear dependence of C -, on V under reverse bias, confirming both the existenceof a Shottky barrier and a barrier height of approximately leV.

Electronic Conduction in Silicon Phthalocyanine Thin Films

“…Those values are found to be 7.72 x10 -5 eV m 1/2 V 1/2 and 5.43 x10 -5 eVm 1/2 V 1/2 for inverse and forward polarization respectively. [19][20] were 60 nm and 120 nm for forward and reverse bias respectively, which are in agreement with values of 70 nm and 100 nm measured in Al-PbPc-Al structures [16].…”

“…ISBN: 0-7803-9230-2 expected and to the values of 1 and 1.03 eV found by other authors [16,19]. Although the C-V curves from the structures could not be drawn, the value of r of the SiPc was calculated from the zero capacitance measurements (at 1 MHz).…”

Investigation of electrical conductivity in Schottky-barrier devices based on nickel phthalocyanine thin films

“…This may be accounted for the terms of nonuniform field in nickel phthalocyanine thin films [19]. Previously several workers [8,16] have interpreted lower-voltage data in terms of Schottky depletion region of thickness, d s , assuming the theoretical value of β s in Eq. (10).…”

“…Abd El-Rahman). trode materials are employed [8][9][10][11][12]. Nickel phthalocyanine, NiPc as one of metal phthalocyanines, has a relatively high value of mobility (∼10 −5 m 2 V −1 s −1 ) [11,12] and thus appears to be a more promising material for application in active devices.…”

Electrical characterization of the organic semiconductor Ag/CuPc/Au Schottky diode

“…The formation of Schottky junctions of organic materials with suitable metallic electrodes has been studied in Refs. [14][15][16][17].…”