Molecular Ordering and the Current-Voltage Characteristics of m-MTDATA Thin Films
Molecular ordering and current-voltage characteristics of vacuum-deposited m-MTDATA(4,4’,4’’-tris[N,-(3-methylphenyl)-N-phenylamino]triphenylamine), widely used as a hole injection material in OLEDs, thin films were investigated. Molecular ordering was induced by thermal annealing under electromagnetic field after deposition of m-MTDATA onto the pre-patterned ITO glass. AFM and XRD analysis were employed to characterize the topology and molecular ordering of m-MTDATA thin films. The XRD and AFM results show that m-MTDATA can be molecularly ordered by means of thermal annealing under electromagnetic field. Thermal annealing at 100°C was desirable to get a high degree of molecular ordering with dendritic grains. It was shown that molecular ordering as well as larger dendritic grains in the thin films influenced on improving the current-voltage characteristics and increasing the leakage current of the ITO/m-MTDATA/Al device. Electromagnetic field improved the surface roughness, as well. It is regarded that Rpv seems more significant than the other roughness parameters. Significantly lower Rpv(peak-to-valley roughness) obtained by both thermal annealing and electromagnetic field resulted in enhancing the stability of the current ITO/m-MTDATA/Al device. Ra(average roughness) and Rrms(root-mean-square roughness), however, did not significantly relate with leakage current.
Byung Tae Ahn, Hyeongtag Jeon, Bo Young Hur, Kibae Kim and Jong Wan Park
S. Oh et al., "Molecular Ordering and the Current-Voltage Characteristics of m-MTDATA Thin Films", Solid State Phenomena, Vols. 124-126, pp. 427-430, 2007