Electric-Field-Assisted Charge Generation and Separation Process in Transition Metal Oxide-Based Interconnectors for Tandem Organic Light-Emitting Diodes
Jin-Peng Yang, Yan Xiao, Yan-Hong Deng, Steffen Duhm, Nobuo Ueno, Shuit-Tong Lee, Yan-Qing Li,* and Jian-Xin Tang*
Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices Institute of Functional Nano & Soft Materials (FUNSOM) Soochow University Suzhou 215123, P. R. China
Graduate School of Advanced Integration Science Chiba University 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan
Center Of Super-Diamond and Advanced Films (COSDAF) City University of Hong Kong Hong Kong SAR, P. R. China
The charge generation and separation process in transition metal oxide (TMO)-based interconnectors for tandem organic light-emitting diodes (OLEDs) is explored using data on electrical and spectral emission proper-ties, interface energetics, and capacitance characteristics. The TMO-based interconnector is composed of MoO3 and cesium azide (CsN3)-doped 4,7-diphenyl-1,10-phenanthroline (BPhen) layers, where CsN3 is employed to replace the reactive metals as an n-dopant due to its air stability and low deposition temperature. Experimental evidences identify that spontaneous electron transfer occurs in a vacuum-deposited MoO3 layer from various defect states to the conduction band via thermal diffusion. The external electric-field induces the charge separation through tunneling of generated electrons and holes from MoO3 into the neighboring CsN3-doped BPhen and hole-transporting layers, respectively. Moreover, the impacts of constituent materials on the functional effectiveness of TMO-based interconnectors and their influences on carrier recombination processes for light emission have also been addressed.