Work function measurement of multilayer electrodes using Kelvin probe force microscopy
Résumé
The workfunction of dielectric vertical bar metal vertical bar dielectric transparent and conductive electrodes, promising candidates for replacing ITO in thin film solar cells, is measured by Kelvin probe force microscopy (KPFM). Measurement on commercial ITO gives a workfunction of 4.74 eV, which is in agreement with the values reported in the literature. Measurements are then performed on optically optimised multilayer electrodes fabricated on glass by e-beam evaporation, using three different dielectrics. For TiO2(37 nm)vertical bar Ag(13 nm)vertical bar TiO2(42 nm), SnOx(45 nm)vertical bar Ag(10 nm)vertical bar SnOx(45 nm), and ZnS(47 nm)vertical bar Ag(12 nm)vertical bar ZnS(42 nm), workfunctions of 4.83 eV, 4.75 eV, and 4.48 eV are measured respectively. These values suggest that these transparent and conductive electrodes are well adapted to extract photo-generated charge carriers in photovoltaic devices in which ITO is normally used. Furthermore, the KPFM technique proves to be an efficient and relatively fast way to determine the work function values of such electrodes.