Mechanism Behind Enhanced Electrical Performance of Doped Nanostructured Tin Oxide - Surface Defect Engineering vs Dopant Electron Donation

Abstract

Tin dioxide (SnO₂), with its high optical transmittance and inherent n-type conductivity, is a promising electron transport layer (ETL) material. For application as an ETL material, it is desirable to enhance the charge carrier concentration and mobility of SnO₂ to maximise its electron conductivity. This is typically achieved by incorporation of dopants which donate electrons into the material. Here we demonstrate that the generation of defects within SnO₂ controls the electrical properties of the doped material. The effects of solely defect engineering are demonstrated by ion implantation of the noble gas Xenon (Xe) into SnO₂. Xe was chosen since it is similar in mass to the well-known chemical dopant antimony (Sb), which simplifies matching of the implantation conditions to cause the same number of ion-induced defects and implanted element distribution, for straightforward comparisons. Our results show that there is no effect of electron donation of Sb, since the resistivities of the film after Xe and Sb implantations are identical. After annealing at 200˚ C, both implanted films show comparable resistivities of (160.8 ± 4.7) μΩ cm and (150.2 ± 8.7) μΩ cm for Sb and Xe, respectively. Differences only emerge at higher annealing temperatures due to the improved stability of defects after Sb doping. Sb doping increases conductivity through defects alone, with no electron donation effects. This will allow for development of better doping strategies to optimise defect engineering and increase performance of SnO₂:Sb for ETL materials.