Electrical and photoelectrical properties of Schottky barrier devices using the chloro aluminium phthalocyanines

Measurements of electrical and photoelectrical properties of Al/ClAlPc/ITO, In/ClAlPc/ITO and Au/ClAlPc/Au are presented. The devices Al/ClAlPc/ITO and In/ClAlPc/ITO show rectification properties, while device Au/ClAlPc/Au does not show rectification properties. These effects are explained in terms of p-type semiconducting behaviour of ClAlPc film and its formation of a Schottky barrier with Al and In electrodes and ohmic contact with ITO and Au electrodes. Under low forward bias (Al and In electrodes are negative with respect to ITO) Ohmʹs law is followed with a thermally activated hole concentration of po = 2.2 × 1017 m−3, a hole mobility μp = 1.2 × 10−6 m2 V−1 s−1 and room temperature conductivity σ = 4.8 × 10−8 (Ω m)−1. At high applied voltage there is a space charge limited conductivity (SCLC) controlled by a discrete trapping level above the valence band edge. The total trap concentration and depth of trap level are 1.4 × 1024 m−3 and 0.78 eV, respectively. Under reverse bias, the conduction process is determined by Schottky emission over a potential barrier of height of 0.65 eV in the low voltage range and the Poole-Frenkel effect for higher voltage. On illumination through the ITO electrode with monochromatic light of 20 mW cm−2 at 660 nm, the device parameters of the Al/ClAlPc/ITO and In/ClAlPc/ITO cells were determined. The experimental absorption and action spectra data are explained with the help of the comprehensive theoretical model proposed by Ghosh and Feng for organic solar cells.