Temperature effect on current-voltage characteristics of molecular organic tris(8-hydroxyquinoline) aluminium complex

The temperature effect on the electron transport in organic semiconducting molecule tris(8-hydroxyquinoline) aluminium (Alq(3)) diodes has been investigated. The current-voltage (J-V) characteristics have been measured in single layer electron only devices with Alq(3) sandwitched between two aluminium electrodes. J-V characteristics have been studied at different temperatures from 295 to 83 K. At high-applied bias and temperatures from 295 to 219 K, our experimental data fits well to the theory where charge transport is determined by exponential traps and J proportional to Vl+1, where l = T-c/T, T-c is the characteristic temperature of traps distribution. A characteristic trap depth (E-t) of 0.19 eV, has been obtained by a temperature dependent analysis of J-V characteristics. However it was not possible to fit the low temperature data below 219 K, with exponential trap theory, without some unacceptable changes. A numerical analysis of mobility model, in which the mobility has field and temperature dependence, has been found in a good agreement to the data below 219 K.