The energy level alignments at the interface between tris(8- hydroxyquinoline) aluminum (Alq3) and ZnO nanowires and thin film were studied with in situ x-ray and ultraviolet photoemission spectroscopy. The changes of work functions, highest occupied molecular orbitals, and core levels were measured with step-by-step deposition of Alq3 on each ZnO substrate. Although both substrates show similar electronic structures, a larger interface dipole is induced at the interface between Alq3 and ZnO nanowires. This results in the reduction of the electron injection barrier at the interface of Alq3 /ZnO nanowires. Thus, the ZnO nanowire substrate is expected to show better performance than that of ZnO film when used as a cathode. We discussed the different interface dipole formation at each interface.
Bibliographical noteFunding Information:
This work was supported by a research project of the Korea Research Foundation (Grant No. 2010-0010007) and Korea Research Council of Fundamental Science and Technology (KRCF) through the KRISS project of “Development of Advanced Industrial Metrology.”
All Science Journal Classification (ASJC) codes
- Physics and Astronomy (miscellaneous)