I currently want to replicate the already published results in terms of 2 step perovskite based solar cells. I have read a few papers in this regard and tried both the spin coating and the dipping methods but still no results.
I am trying to fabricate the inverted structure i.e. ITO/PEDOTT:PSS/Perovskite/ PCBM/Al.
what I'm doing is spin coating PbI2 (460mg/ml) in DMF, at 3000 rpm for 15 s, followed by dipping in MAI (10mg/ml) for 3 mins. (as per literature). Under the naked eye the dark reddish brown perovskite film formed as it should (similar to single step) how ever no results.
Kindly guide how to proceed further.
p.s. I have tried this structure for the single step method and have achieved near 11%.
I'm not familiar with this architecture but I am familiar with the 2 step deposition. I would advise a longer dip time, around the 20 - 30 minute mark. I personally dip for 30 mins with MAI in IPA at the same concentration.
Muhammad,
The same problem has been dissected in a forum on the researchgate. Please to follow the discussion refer to the Link: https://www.researchgate.net/post/In_the_two-step_synthesis_of_perovskite_solar_cells_why_does_the_perovskite_layer_go_off_evaporates_after_removing_from_CH3NH3I-Isopropanol_soln
My advise to you is to evaluate the result of every technological step. Do, not move to the next step except the current step is succeeded. It is not sufficient to say that you saw a dark brown color with your naked eyes. It is so that you have to make an annealing step after the spin on PbI2 (460mg/ml) in DMF. The PbI2 must be completely developed before going to the next step. This what you will get from the above link>
your dipping time is very short. it must be at least 30 minutes. I personally dipped in MAI for 1 hour. penetration of MAI to PbI2 needs a long time.
Dear Muhammad,
You can refer to my previous works on perovskite formation and NiOx HTL as follows.
(1) A Smooth CH3NH3PbI3 Film via a New Approach for Forming the PbI2 Nanostructure Together with Strategically High CH 3 NH 3 I Concentration for High Efficient Planar-Heterojunction Solar Cells, Advanced Energy Materials 5(23):1501354.
(2) Pinhole-free and Surface-Nanostructured NiOx Film by Room-Temperature Solution Process for High-Performance Flexible Perovskite Solar Cells with Good Stability and Reproducibility,ACS Nano, 2016, 10 (1), pp 1503–1511.
Hope it helps. Good luck.
Best Regards,
Hong
Dipping time depends on concentration of precursors but for your case it normally should be more than 20min. You also should keep in mind long dipping time causes rough and undesirable crystal on top of perovskie layer.
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