Electric-field-assisted charge generation and separation process in transition metal oxide-based interconnectors for tandem organic light-emitting diodes

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 properties, interface energetics, and capacitance characteristics. The TMO-based interconnector is composed of MoO ₃ and cesium azide (CsN ₃)-doped 4,7-diphenyl-1,10-phenanthroline (BPhen) layers, where CsN ₃ 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 MoO ₃ 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 MoO ₃ into the neighboring CsN ₃-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.