Electrical and optical properties of new azo dyes derived from m-aminophenol

•The XRD diffraction patterns confirm the polycrystalline phase.•All azo derivatives (HLn) have semiconductor behavior.•The operating dc conduction mechanism is the VRH for all samples.•Both of the ac conduction mechanisms SPT and QMT are observed.•The variation of substituent group strongly affects the value of Eg.

The electrical and optical absorption properties of 5-amino −2-(aryldiazenyl) phenol (HLn) was investigated. A semiconductor behavior with two thermal activation energies for dc conduction which are in the range 0.11-0.47 eV for ΔE1 at the lower region of temperature and 0.77-1.12 eV for ΔE2 at higher region of temperature are observed. The ac conductivity measurement showed a dependence of σac on test frequency following the relations σac∝ωS. Temperature dependence of the exponent S recommends different conduction mechanisms depends on the chemical structure. The recommended mechanism are small polaron tunneling (SPT) and quantum-mechanical tunneling mechanism (QMT). The optical absorption investigations for HLn thin films show that the ligands HL1 and HL2 experiences indirect optical transition with energy gap 2.02 and 1.89 eV, respectively. The ligands HL3 and HL4 experiences direct optical energy gap with values 2.6 and 2.20 eV, respectively.