PhD Defence by Eduard Llorens Balada

Principal supervisor 

Dr. Technices Eugen, Stamate  

Examiners

Professor David Horwat, University of Lorraine
Professor Morten Madsen, SDU 

Chairperson at defence

Senior Researcher Alice Bastos da Silva Fanta, DTU

Abstract

As technology develops, society constantly seeks ways to become more sustainable and efficient. New materials play an important role in current and future devices like smart windows, solar cells, and touch screens. This study was focused on the deposition of thin film nanomaterials made of metal oxides, by investigating their properties, to improve the functionality and efficiency of optoelectronic devices.

The main technique used to obtain thin films is magnetron sputtering, a plasma-based method that allows one to deposit uniform layers with high quality and tuned composition and functionality.

Three innovative nanomaterials have been studied. The first was aluminum-doped zinc oxide (AZO). It is one of the few thin films that exhibits high electrical conductivity while being transparent, hence it is used in solar panels, smart windows and touchscreens. The second is vanadium dioxide (VO2), considered a complex material due to its ability to change from being an electrical insulator to a conductor when heated above 68°C. VO2 is one of the most promising thermochromic materials due to its ability to change its color and transmittance as function of temperature. Lastly, tungsten trioxide (WO3) was studied due to its electrochromic properties. WO3 can reversibly change its color and transmittance depending on the applied voltage, a fact that makes it important for windows able to adjust their transparency to sunlight, thus minimizing the use of air conditioning or heating devices, and therefore saving energy.

The conducted research revealed the optimal deposition method to obtain state-of-the art AZO thin films over a 150 mm in diameter glass substrate; elucidated the role and importance of an AZO interface layer when depositing VO2 and WO3; and explored the additional layers needed to accommodate the VO2 on AZO.