AC Impedance Spectroscopy Studies of PtPc Doped Alq₃ Thin Film

Abstract

The Platinum phthalocyanine (PtPc) was doped in Tris (8-hydroxyquinolinato) aluminum (Alq₃) for tailoring the electrical and optical properties. The electrical properties of the optimally doped Alq₃ thin film based on different device application were studied extensively by AC impedance spectroscopy. The absorption peak of the thin film was observed at 381 nm and 598 nm that correspond to the absorption of Alq₃ and PtPc, respectively. The photo-luminescence intensity (PL) peak of thin film excited with wavelength 380 nm was found at 510 nm. The electron mobility calculated from trap-free space-charge limited region (SCLC) of current-voltage characteristics is 0.3 × 10⁻⁷ cm² V⁻¹s⁻¹. The frequency dependent impedance spectra show single relaxation process. The Cole-Cole plots indicates that the PtPc doped Alq₃ thin film can be represented by a single parallel resistance R _P and capacitance C _P network with a series resistance R _S . The values of R _P decreases with increase of applied bias. The variation of AC conductivity (σ _ac ) with frequency shows two different region viz frequency dependent and frequency independent.