Can some one please inform how to acquire J-V curves for perovskite solar cells?Fabricated structure is ITO/PEDOT:PSS/Perovskite/PCBM71/Al. The perovskite precursor used here is equimolar PbI2:MAI in DMAC solvent. I tried taking J-V curves by sweeping forward (0 to +1.2V)/reverse scan (+1.2V to 0) with different step size (voltage) and sweep delay (tried many variations). However, proper J-V curve could not be acquired. Is this structure correct (ITO/PEDOT:PSS/Perovskite/PCBM71/Al)?
Also, how to choose proper step voltage size and sweep delay?
The structure should ideally work. But there are more parameters required to access your situation than what you have provided. Setting a step size of 10 mV and sweep delay of 300 mV/s should be fine. Did you get a short or a diode characteristic? The major problem can come from Al shorting through PCBM. You could use LiF or Ca to protect your ETL. Also there are parameters like how you had deposited perovskite, what is the storage time and how you have stored the device before measuring. But i believe depositing Al on top PCBM can be a bit tricky and it would help to use Ag to start with.
Thank you Anand. I didnt get any diode characteristics while scanning both forward and reverse scans. As you told PCBM/Al interface is a problem. I believe perovskite film formation the other day should be fine. Deposition we used is spin coating from DMAC solvent and spun at high speed rpm of 5000 (30) sec
Do you think either Ag or Au gold deposition atop PCBM should be fine? Please comment
Here,I found an article using PCBM/Al and still showing great PCE. Please have a look at :
http://www.nature.com/ncomms/2015/150617/ncomms8348/full/ncomms8348.html?message-global=remove
Hi Sai,
It should ideally work like Anand said. In planar and especially in inverted perovskite solar cells the morphology plays an important role. Please see the SEM and XRD to confirm you have perovskite phase and smooth and compact morphology. It would help if you post the curve so that we can see. Also please post the humidity levels while fabrication as they might influence the conversion and morphology.
Regards,
Swami
Thank you Swami for the comments. Last time, the relative humidity was ~25 to 30%. I tried taking J-V curve by soaking under simulated light for ~ 1 min, however very poor characteristics was noticed. Next time, I will post J-V curves.
Hi Sai, Yes, to start with the surface coverage, humidity and conversion are huge factors influencing your performance as swami said. So it would be wise to make sure every aspect of the film is fine before starting the device fabrication. I checked the article, it is absolutely fine to use Al;but with non uniform coverage and faster diffusion rates of Aluminium it becomes very difficult to optimize the device. While evaporating Al you do use limited rate with a monitor right? Else try Ag to some extent to begin, a little lessw nasty :)
Thanks for the reply Anand. We have manually operated Al thermal evaporator in common clean room (its too old) and at times, the deposition is not very controllable. So, this time I would try Au deposition (with the same conditions) to compare the device performance. Would you please inform whats short characterisitcs?
Sai, I would suggest not to use Au if you are using PEDOT-MAPI-PCBM configuration. The work function of Au is too low and might induce huge offset losses in VOC when coupled with PCBM as an ETL. However it would be minimal when Ag is employed.
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