Recently, I looked through some literatures about solar cells, which mensioned" Using N2 flow for drying the cleaned FTO glass". Can we use air for drying FTO glass or other substrate like Si or common glass covered by thin film grew before? Is there any reaction between FTO film and air?
Air is not good as N2 because, the oxygen and other components may react with the substrate while nitrogen should not make any chemistry on your surface.
Dear Johannes,
Thanks for your answer. But can FTO(SnO2:F) react with air(or O2, H2O) at room temperature? If not, then it's not necessary using N2 flow to dry the FTO, and air is more convenient.
Here provide some new opinions which I puzzled out this morning, in order to get more valuable ideas:
Firstly, Intrinsic ion crystal tin oxide(SnO2) has certain lattice defects, namely the oxygen vacancies, so the SnO2 has electronic conductivity properties.
Then, the FTO is F doped tin oxide, also a kind of N-type semiconductor materials. Its majority carrier is electron, mainly origins from O vacancies of SnO2, and electrons provided by the doped impurity (F).
The H2O and O2 in the air tend to adsorb on the surface of FTO, which may combine with oxygen vacancies and dissociate into active hydroxyl[·OH], perhydroxyl radical [·OOH] and hydrogen peroxide [H2O2]. The generated reactive group on the FTO surface with strong redox property can further react with the organic pollutants in the air, presenting as to attack the unsaturated bond or extracts atoms of the pollutants.
Hi Zhiqiang Yu, H2O and O2 adsorbed on the surface of metal oxides can dissociate and react with organic vapors, which is the basic principle behind metal oxide sensors for VOCs. However, this is only possible at elevated temperatures Please refer for example,
Chem. Mater., 2005, 17 (15), pp 3997–4000; Sensors and Actuators B: Chemical,Volume 12, Issue 1, 15 March 1993, Pages 71-75
Hi Harinarayanan,
Thanks a lot for your useful answer. From the literatures you suggested I knew that, the gas detection mechanism of SnO2 thin-film is based on the reversible change in conductivity of the surface of SnO2 grains, and it really need a high temperature to drive the reactions.
So, in our case of using N2 flow to dry the FTO glass, the reason may not as complex as I mentioned above. It may aiming for the preventing of pollutants in the air simply.
- Badges
- Science topic
- Similar topics
- Physical Sciences
- Materials Science
- Thin Films and Nanotechnology