Effect of Oligothiophene as a Buffer Layer on the OLED of the Convergence Relation with Varying Thickness

Abstract

Abstract. Background/Objectives: In this article the buffer materials, α-6T and α-7T are used to study the interface of metla/organic in OLEDs. It has been observed that the electrical, light emitting and efficiency properties are strongly depend on the thickness of the buffer layer with 60nm of α-6T and 3nm of α-7T the mostly improved properties were observed. Methods/Statistical analysis: The physical interaction of molecular at the metal/organic interface has been investigated by contact angle hysteresis. The surface energy of oligothiophene layer on ITO electrode varies within 10mJ/cm2. The polar component of surface energy of organic materials(HTL)
on buffer layer materials was observed to be independent on the thickness of buffer layer with the value of zero. The strong electrostatic force of the metallic surface may lead the properties of organic materials to be different from that of natural state. However the buffer layer may contribute to the continuously layered similar energy state that increase the efficiency of hole injection.
Findings: It has been observed that the electrical properties, light emitting and efficiency properties are strongly depend on the thickness of the buffer layer with 60nm of α-6T and 3nm of α-7T the mostly improved properties were observed. The lowered energy barrier, about 0.2 ~ 0.4eV, for hole injection at the interface of metal/buffer layer and the improved surface morphology of hole injection surface may contribute to the improvements. It was expected that the increase of the absolute number of holes injected might increase the light emitting efficiency and it was observed. Improvements/Applications: As a tool to investigate such as phenomena, the use of buffer materials gives advantages. The buffer materials normally show stable chemical and physical properties, it could be avoided the destruction of original electronic state during the measurement. The use of buffer materials and the understandings of interface phenomena could offer many applicable products to our common life.