I am doing my thesis on Perovskite solar cells. I am trying to prepare triple cation cells, but the color of the cells after deposition is milky, which I think would be due to wrong solution preparation. I prepared the FAMA solution consisting 172 mg FAI, 508 mg PbI2, 80.7 mg PbBr2 and 22.4 mg MABr in 800 micro liter DMF and 200 micro l DMSO. and the Cs solution with 389.7 mg CsI in 1 ml DMSO. Combining both solution by mixing 50 micro l Cs Solution in 1 ml FAMA solution. I deposited 80 micro l of the final solution on the substrate via Spin coating (2 step: 1st 1000 rpm for 10s and 2nd 4000 rpm for 30s). Used 500 micro l Chloro benzene as anti-solvent 20s before the end of 2nd step. Also it seemed that the solution didn't adhere to the glass substrate as it should.
Try the following suggestions to see if it helps:
1. You might need to prepare the FAPbI3 and MAPbBr3 solutions seperately and subsequently mix them before you add the CsI solution.
2. The 'milky' apperence of your film may be related to the surface morphology with low uniformity and large pinholes. You can try to vary the loading time of the antisolvent (CB for your case) to get a mirror-like black film. For instance, the loadding time could be 25, 20, 15 or 10 s before the end of the 2nd step spin-coating, which is related to the film preparation condition such as temperature or vapor atmosphere.
3. Make sure that your substrate is thoroughly cleaned. Repeatal sonication in solvents and UV Ozone treatment would help here. The 'not adheresive' problem might be originate from a 'dirty' substrate.
All the best
Ke
Hello, sorry for the late reply. Thank you for your recommendation. I followed the process and have been able to prepare good samples.
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