I'm fabricating CsSnBr3 perovskite thin film using spin-coating method.
I used CsSnBr3 in DMF solution and chlorobenzene was added as a anti-solvent method
After water, methanol and acetone cleaning glass substrates, to increase wettability between DMF and glass substrates, uv-ozone treatment was performed 15minutes.
But fabricated film is too thin and I couldn't find any absorbance spectra peaks.
By decreasing to 1500rpm it looks dark brown but still not uniform and no xrd peaks.
In this view, I'm considering oxygen plasma treatment to increase the wettability DMF and substrates. I guess it's not common to do it for perovskite film instead of UV-ozone treatment.
Please teach me appropriate condition of oxygen plasma treatment to replace uv-ozone. Or is there any other method to increase wettability?
please refer to the attached experimental details
Dear Hanbo Jung,
What about the concentration of your solutions? The concentration of a solution for a spin-coating film is one of important factors to make variable film thickness. In your case, what is the concentration of your solutions?
It was found that plasma treatment could have similar effects on a substrate after optimising the power and duration.
The typical power and duration for a plasma treatment on a glass substrate are above 60W and 3 mins, respectively.
Xuhua Wang The concentration is 0.6M CsSnBr3 in DMF. So it is better for me to use above 60W and 3 mins, respectively. Thank you.
Dear Hanbo Jung,
Thank you for asking this interesting question.
From the pictures you have shared, it is clear that you are trying to deposit perovskite precursors from the spin-coating method. In addition to what Miss Xuhua Wang has said, I would like to bring your attention to the method of spin-coating. What sort of spin coating method are you using? dynamic or static?
Usually, for beginners, it is quite difficult to get good control of precursor dripping in the dynamic spin-coating method. In that case, I would suggest trying the static spin-coating method and fully wet the glass substrates using the tip of your micropipette before the start of the process. Moreover, these patterns have been observed after antisolvent drippings for beginners. I am afraid you have to perform experiments continuously to get a good practice of dripping solvent from an optimal height.
Good Luck with your research!
Kind Regards,
A. Sattar Chaudhry
It depends on many things, but the important ones are surface wettability and the concentration of the solution. Could you please specify these? You should properly clean the substrate and should have 1 molar solution. The speed you have used is smaller. It should have good coverage.
Abdul Sattar Nasir Ali I tried static spin-coating and I used 0.8M CsSnBr3 perovskite solution (DMF:DMSO=8:2) and dripped 100ul of it among 1000ul and added 300ul of chlorobenzene at the last 10seconds. My spin-coating rpm was 2000 for 30s. I think 100ul is not enough to fully wet the 3.5X3.5cm^2 glass substrates. I will try increasing the amount of solution.
Dear Hanbo Jung,
I think 100 ul is far more than enough for your substrate size since extra precursor will only result in material wastage and will fly off at the start of the spin coating. We usually use 20 ul for 20 mm x 20 mm substrate size and spread the precursor with the tip of the micropipette to wet the complete substrate surface, for static spin coating, using approximately 225 ul chlorobenzene as antisolvent.
Further, In my opinion, in your experiment, the problem lies in the antisolvent dripping technique. This is a very crucial step. You need to be extra careful to maintain a certain height between substrate and tip of the micropipette and smooth dripping of the antisolvent. Because if you drop the antisolvent from more than 1-2 cm height it will try to throw off your material from the substrate in my experience. Please check this video presentation by Michael Saliba as well. I hope this will help. Good Luck!
https://www.youtube.com/watch?v=DdKd0EjO1XQ&t=1165s&ab_channel=nanoGeConferences
Kind regards,
Abdul Sattar
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