Study of electrical transport properties of ZnO thin films used as front contact of solar cells

This work is focused on the study of possible mechanisms affecting the electrical transport properties of ZnO thin films. The films were deposited using the reactive evaporation technique, obtaining transmittances greater than 80% and resistivities of the order of 8 x 10(-4) Omega cm without using extrinsic doping. This films are suitable for transparent front contact of solar cells. Measurements of resistivity and Hall coefficient, as a function of temperature, were performed on the films. The interpretation of these results was done with the help of a theoretical calculation of the carrier mobility as a function of the temperature. Several scattering mechanisms affecting the electrical transport in the temperature range studied (90 K-680 K) were found. The most important are processes occurring in the grain boundaries and interactions of free carriers with ionized impurities. (c) 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.