Fine tuning work function of indium tin oxide by surface molecular design:Enhanced hole injection in organic electroluminescent devices

Characteristics of electroluminescent (EL) devices were improved dramatical ly using indium tin oxide (ITO) chemically modified with H-, Cl-, and CF3-t erminated benzoyl chlorides. By the use of reactive -COCl groups, ITO surfa ces were modified quickly and the work function of the modified ITO was cha nged widely depending upon the permanent dipole moments introduced in the p ara- position of benzoyl chloride. We also compared the performance of the EL devices with ITO modified with different binding groups (-SO2Cl, -COCl, and -PO2Cl2) of p-chlorobenzene derivatives. Finally, we examined the corre lation between the change in the work function and the performance of the E L devices by the chemical modification and found that the enormous increase in ITO work function up to 0.9 eV is possible using phenylphosphoryl dichl oride with a CF3-terminal group in the para-position. (C) 2001 American Ins titute of Physics.