Effectiveness of Annealing on the Structural, Electrical, and Optical Properties of Erbium(III)-tris(8-hydroxyquinolinato) Films for Possible Use in OLEDs

In this study, Erbium tris-8-hydroxyquinoline (Erq 3 ) thin films were deposited on a cleaned glass substrate using the thermal evaporation technique and then thermally annealed up to 523 K. The morphology, optical and electrical properties were investigated for as-deposited and annealed thin films. The grain sizes observed by AFM of the Erq 3 thin films vary between 80 and 130 nm. The average surface roughness of the Erq 3 thin films was seen to range between 46 and 65 nm. The increase in the annealing temperatures leads to an increase in the average crystallite size by about 60%. The evolution of the electrical and optical properties of our prepared thin films due to the annealing process was correlated with their structural properties. According to Tauc’s theory, a slight increase in the energy gap by about 0.17 eV due to the annealing process was recorded. The nonlinear parameters of Erq 3 such as χ3 and n 2 decreased by about 41% and 45% due to the increase of the annealing temperature up to 523 K. The increase of the annealing temperature up to 523 K leads to the decrease of the nonlinear coefficients of Erq 3 due to the decrease of the localized defect states.