Hi, I'm a new researcher in perovskite solar cells. Recently I'm working on the basic perovskite solar cell fabrication using SnO2 as ETL. My device is planar structure with CsFAMA recipe and sprio-OMeTAD as HTL. I use "Tin(IV) oxide, 15% in H2O colloidal dispersion" from Alfa Aesar as ETL precursor and dilute it with water (1:7). Then spin coat it on FTO by 4000 rpm (dynamic spin coating). However the problem I met is that this ETL recipe dies not always work. On only one batch, I got good performance (> 15%). On other occasion, the ETL showed short circuit which makes the device fail. I repeated several times and it turns out the problem comes from SnO2. Because every device on TiO2 ETL works.
Here I sincerely ask some points that I need to pay attention to during Tin oxide ETL preparation from experienced researchers. Is my concentration too low? (If so, I still made one batch works.) Do I need long ultrasonication time? Could I filtrate the solution with 0.22 μm PES filter? Is there some thing I missed during the ETL fabrication? Because from the literature, the information is limited: "For SnO2 nanoparticles films, the diluted SnO2 nanoparticles
solution (2.67%) was spin coated on glass/ITO substrates in ambient air, and then annealed at 150 C for 30 min".
Thank you for the help.
Alec Ji In this type of work (substrate and chemicals) cleanliness is next to godliness. I assume you're working in Class 100 conditions with all liquids and chemicals filtered to 0.02 um or better. I have only used (Headway) spin coaters within a clean room - never outside. You need to ensure that the liquids will wet whatever substrate you're spinning on to - that may involve a change of solvent or the use of a surfactant to lower surface tension.
Short circuits (and pinholes) are usually down to some contaminant in the liquids or an unclean substrate. Cleaning glass substrates is very important and I've published on RG a recipe on this (derived from the LCD industry) that was highly successful. This is the url:
https://www.researchgate.net/post/What_is_the_best_way_to_clean_ITO_coated_glass_substrate
Alec Ji hello, I'm a new researcher in perovskite solar cells. I had a same recipe and problem your experiment. now you fix it? if so, Could you advice for me? please..
p.s PTFE filter is better than PES filter
this is the reference.
Dear Ji and Kim,
The UV-Oz treatment is important process for deposition of SnO2. Also, ITO works better than FTO in the case of SnO2 is being used as ETL.
Bests,
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