Doped copper phthalocyanine via an aqueous solution process for high-performance organic light-emitting diodes

Efficient carrier injection plays an important role in realizing high performance organic light-emitting diodes (OLEDs). Herein, we discuss the development of an efficient and stable hole injection layer (HIL), 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodim ethane (F4-TCNQ) doped copper phthalocyanine-3,4′,4″,4‴-tetra-sulfonated acid tetra sodium salt (TS-CuPc) via a solution process, in OLEDs. The p-type-doped TS-CuPc film demonstrates an improved hole mobility and a better surface morphology with the help of F4-TCNQ. By the F4-TCNQ tailoring, the composite film forms a cascade energy level alignment, which would effectively facilitate hole transport. In addition, the aqueous solution processed TS-CuPc:F4-TCNQ precursor is close to neutral with good stability for avoiding the electrode erosion. As a result, the fabricated OLEDs employing TS-CuPc:F4-TCNQ as HIL show a maximum power efficiency of 46.4 lm W−1, which is significantly higher than the conventional device based on poly (3,4-ethylenedioxythiophene):poly (styrene-sulfonate) (PEDOT:PSS) which has a maximum power efficiency of 26.3 lm W−1.