Permittivity-engineered transparent conducting tin oxide thin films: from deposition to photovoltaic applications

Abstract

The materials, optical and electrical properties of transparent conducting tin oxide-based thin films are investigated, with particular emphasis on their application to photovoltaics. Thin films of transparent conducting oxides are used as transparent electrodes in all thin film solar cells. However, the films contribute optical and electrical losses of their own. In this work, the fundamental aspects of increasing permittivity in transparent conductors are investigated by adding ZrO2 (a high permittivity material) to SnO2 films (a transparent conductor). The experimental results are explained by expectations from the Drude model for free electrons. Details and results for the film synthesis by chemical vapor deposition are explored. Results for decreased optical absorptance are presented together with evidence for increased permittivity. Additionally, experiments indicate that increasing permittivity also has the benefit of increasing carrier mobility when in the limit of ionized impurity scattering.