TY - JOUR

T1 - Aluminum-doped zinc oxide sol-gel thin films: Influence of the sol's water content on the resistivity

AU - Nehmann, J.B.

AU - Ehrmann, N.

AU - Reineke-Koch, R.

AU - Bahnemann, D.W.

N1 - Copyright: Copyright 2014 Elsevier B.V., All rights reserved.

PY - 2014/4/1

Y1 - 2014/4/1

N2 - Thin films of indium tin oxide (ITO) have gained substantial interest due to their optical and electrical properties. Since ITO is an expensive material and indium is a rare element, considerable attempts have been made to replace it by, e.g., aluminum-doped zinc oxide (ZnO:Al). The production of ZnO:Al is less cost-intensive, especially if the sol-gel technique is applied, while its properties are comparable to those of ITO. In this study, we demonstrate that the electrical properties of ZnO:Al thin films can be improved considerably by the addition of small amounts of ultrapure water to the dip coating solution during the preparation. The lowest resistivity obtained with a film prepared from a sol containing 0.2 M water is 2.8·10 -3Ωcm. Optical modeling thus indicates an improvement of the free carrier mobility of films prepared from sols in the presence of additional water. The films prepared have an average thickness of 340 nm and a solar transmittance above 85% after annealing in a forming gas atmosphere. Clearly, the addition of water to the sol has a positive impact on the resistivity of the final ZnO:Al thin film. We suggest the observed increase of the free carrier mobility to be due to an improved electron transfer at the grain boundaries between the spherical nanoparticles.

AB - Thin films of indium tin oxide (ITO) have gained substantial interest due to their optical and electrical properties. Since ITO is an expensive material and indium is a rare element, considerable attempts have been made to replace it by, e.g., aluminum-doped zinc oxide (ZnO:Al). The production of ZnO:Al is less cost-intensive, especially if the sol-gel technique is applied, while its properties are comparable to those of ITO. In this study, we demonstrate that the electrical properties of ZnO:Al thin films can be improved considerably by the addition of small amounts of ultrapure water to the dip coating solution during the preparation. The lowest resistivity obtained with a film prepared from a sol containing 0.2 M water is 2.8·10 -3Ωcm. Optical modeling thus indicates an improvement of the free carrier mobility of films prepared from sols in the presence of additional water. The films prepared have an average thickness of 340 nm and a solar transmittance above 85% after annealing in a forming gas atmosphere. Clearly, the addition of water to the sol has a positive impact on the resistivity of the final ZnO:Al thin film. We suggest the observed increase of the free carrier mobility to be due to an improved electron transfer at the grain boundaries between the spherical nanoparticles.

KW - Chemical solution deposition

KW - Forming gas

KW - Free carrier mobility

KW - Hydrolysis

KW - Resistivity

KW - Sol-gel

KW - ZnO:Al

UR - http://www.scopus.com/inward/record.url?scp=84896404227&partnerID=8YFLogxK

U2 - 10.1016/j.tsf.2014.01.052

DO - 10.1016/j.tsf.2014.01.052

M3 - Article

VL - 556

SP - 168

EP - 173

JO - THIN SOLID FILMS

JF - THIN SOLID FILMS

SN - 0040-6090

ER -