Electrode modifications, OLEDS

The work function control by alloy formation [588-592] and by the surface modification has been applied to enhanced charge injection at electrodes for OLEDs [306-313, 324, 325], electrochemical [314] and photovoltaic (PV) cell studies [308,... 

Unlike the constraints on anode material, the constraints on cathode materials are usually lower because typically they do not need to constitute the transparent electrode material. In certain instances, where a completely transparent OLED is needed (windshield and heads-up displays), ITO may also be used as the cathode with suitable modification [12]. In general, cathode materials are pure metals or metal alloys. The requirements for cathode materials are as follows ... 

The most commonly encountered TCO electrodes, typically studied as thin films, are antimony-doped tin oxide (ATO) or fluorine-doped tin oxide (FTO), ITO, titanium oxide (anatase or rutile, Ti02), and zinc oxide (ZnO) [19], There are also some recently reported trinary and ternary oxides based on modifications of ITO, zinc-indium tin oxide, ZITO or IZTO, for example, which may become more popular with time as electrodes for solution-based redox chemistry and as anodes in devices such as OLEDs and OPVs [7], These new tailored composition oxides may exhibit higher stability, higher work functions, and/or a greater variety of surface sites with more possibilities for chemical modification. 

Chlorosilanes are often used to aid in the extensive cross-linking that is desired for the modification of anodes for use in OLED devices. Chlorosilanes liberate HCl as a by-product of silane attachment, which can degrade the TCO surface if low concentrations of base are not added for neutrali2ation. No significant etching of the TCO anode surface has heen noted, and surface analysis of the modified electrode generally indicates no entrapped chlorine [14,51-53]. 

---