Effects of Substrate Temperature on the Properties of Alq₃ Amorphous Layers Prepared by Vacuum Deposition

Abstract

In this study, various Alq 3 amorphous layers are prepared by vacuum deposition at different substrate temperatures T sub . The surface morphology, structural information, and electrical and optical properties of these as-deposited layers are studied by atomic force microscopy, X-ray diffraction, J-E curves, and photoluminescence studies, respectively. The optimum deposition conditions for Alq 3 amorphous layers with respect to T sub are also discussed.

Crystallization of Amorphous Tris(8-hydroxyquinoline)aluminum Nanoparticles and Transformation to Nanowires

“…The phenomenon of increased PL intensity is in agreement with previous reports, which revealed that increasing the substrate temperature or annealing process for an AlQ 3 film could lead to a higher PL intensity, [26][27][28] except in the case of reduced intensity reported by Papadimitrakopoulos and co-workers. [29,30] Compared to curves c,d, the lower intensity of curve b can be attributed to incomplete transformation and less crystallization in 1 min.…”

Effects of source and substrate temperatures on the properties of ITO/CuPc/C60 heterostructure prepared by physical vapor deposition

“…From a crystal grower's point of view, during PVD processes, both T sou and T sub markedly affect the qualities of the asdeposited films, and these effects were clearly exhibited by our earlier experimental results on C 60 polycrystalline films [19,20] and tris(8-hydroxyquinoline)aluminum (Alq 3 ) amorphous layers [21,22]. To extend these experimental findings from a single layer structure to a sophisticated and complicated optoelectronic heterostructure, the effects of T sou and T sub on the performance of OPV cells with a heterostructure of ITO/CuPc/C 60 /Ag prepared by PVD were studied.…”

Effects of isomeric transformation on characteristics of Alq3 amorphous layers prepared by vacuum deposition at various substrate temperatures

“…Further details of the deposition processes have been presented elsewhere. 14 For electrical characterization, a top Au-metal contact with an active area of approximately 4 ϫ 4 mm 2 is fabricated by ion sputtering. A current-voltage ͑I-V͒ measurement is applied to the sandwiched Au/organic-layer/ITO configuration.…”

“…In addition, to obtain the actual magnitude of electric E field across the organic film, a correction with respect to the internal resistance of the measuring circuit is carefully taken into account. In low E fields from 0 to 0.75 MV/m, the measured current-density versus E field ͑J-E͒ curves of all of the samples exhibit linear Ohmic behavior, 14 from which the dark electrical conductivity of the organic Alq3 layer is then estimated. To eliminate effects from water vapor and oxygen gas, all the measurements are made after the sample is put into a cryostat system in dynamic vacuum for at least 12 h. During that period, data are taken to test their stability and reliability at 300 K. Experimental results reveal that, after 12 h in a dynamic vacuum, the dark electrical conductivities ͑T = 300 K͒ of the amorphous samples reach an almost steady state.…”

“…12,13 From external control and monitoring of T sub and T sou , our earlier experimental results demonstrated that, when T sou is fixed at 250± 5°C, T sub strongly affects the surface morphology, structural information, and electrical and optical properties of the as-deposited Alq3 amorphous layers. 14,15 An anomalous T sub dependence of the surface and electrical properties was also observed for Alq3 amorphous layers deposited at T sub between 90 and 120°C. 15 In this paper, to explain these anomalous experimental results, we propose that the vacuum deposition of Alq3 with T sub between 90 and 120°C involves a thermal interconversion between mer and fac Alq3 isomers.…”