Synthesis of carboline-based host materials for forming copper(I) complexes as emitters: A promising strategy for achieving high-efficiency and low-cost phosphorescent organic light-emitting diodes

Abstract We have designed and synthesized two α-carboline-based host materials, 1,3-bis(9H-pyrido[2,3- b ]indol-9-yl) benzene (mCaP), 2.6-bis(9H-pyrido[2,3- b ]indol-9-yl) pyridine (26mCaPy) and two δ-carboline-based host materials, 1,3-bis(5H-pyrido[3,2- b ]-indol-5-yl) benzene (mCdP), 2,6-bis(5H-pyrido[3,2- b ]indol-5-yl)pyridine (26mCdPy). Their photophysical and electrochemical properties have been fully investigated. It has demonstrated that the photoluminescent quantum yields of δ-carboline-based materials are significanly superior to those of α-carboline-based materials. Carboline unit could coordinate with copper iodide (CuI) to form copper(I) (Cu(I)) complex by co-depositing. Co-deposited films of these carboline derivatives and CuI were fabricated as an emissive layer of the organic light-emitting diodes. Consequently, the device with co-depositing mCdP and CuI as an emitter gave a maximum current efficiency of 37.3 cd A −1 , a maximum power efficiency of 26.3 lm W −1 .