Comments on: “Gallium-doped ZnO thin films deposited by chemical spray”

In this communication, I will discuss some aspects concerning a paper recently published by H. Gomez et al. on the properties of gallium-doped ZnO thin films deposited by chemical spray methods [H. Gomez, A. Maldonado, M. de la L. Olvera, D.R. Acosta, Sol. Energy Mater. Sol. Cells 87 (2005) 107.]. I believe that there are some wrong considerations of basic principles, some incorrect experimental procedures and inconsistencies on the analysis and throughout the paper. The “Introduction” reflects some knowledge on the subject, but it seems that the authors of the aforementioned paper use outdated background sources in some cases, and inconsistently apply prior research in others. The “Experimental procedure” shows some serious lack of knowledge concerning thin films that are potentially applicable as transparent electrodes in photovoltaic devices. In the “Results and discussion”, I found some of the arguments and statements contradictory, mainly when the effects of their vacuum annealing were being discussed. Considerations on the “Structural properties” are necessary, as they are not appropriate for comparative purposes. Finally, a last point, but not less important than the others, is the “Conclusions” of the paper. Some suggestions are made below for the improvement of this, and several others, aspects of the paper.