Improved organic light-emitting device with tris-(8-hydroxyquinoline) aluminium inserted between hole-injection layer and hole-transporting layer

摘要

A layer of tris-(8-hydroxyquinoline) aluminium ( Alq(3)), which is normally used as an electron-transporting and emissive layer, was incorporated between the hole- transporting layer and the hole- injection layer to balance the electron - hole injection. The Alq3 layer performed to block the hole current which is a majority carrier in a typical organic light-emitting device. An increase in current efficiency by almost 30%, from 3.1 to 4.0 cdA(-1), with a minimum voltage shift was achieved with a 2 nm Alq(3) layer as a hole- blocking layer. A reduction in HTL thickness was observed to reduce the efficiency due to electron leakage to the HIL, whereby an inefficient exciplex emission was observed.