My fill factor of perovskite solar cells used to be 50~60%. All of a sudden, the I-V curves look like a straight line and sometimes there is a S-shape. The fill factor is close to 25% and even lower than 25%. Nothing has been really changed. The Jsc and the Voc are even better than before. The Jsc used to be lower than 10mA/cm2 and now it is higher than 15mA/cm2. The Voc used to be around 0.85V and now it is around 0.95V. The structure is FTO/TiO2/peorvoskite/spiro-MeOTAD/Au. The spiro-MeOTAD was prepared and stored in the freezer 2 months ago. Your suggestions are highly appreciated!
Hi, Dear Samad,
Thank you for your suggestions. However, I do not think any of the steps could be able solve my problem. I still doubt the 3-month old spiro-MeOTAD could be problem. I am going to prepare new spiro-MeOTAD solution and fabricate the solar cells again using same procedures. I will let you know my progress. Bless me!
Hi Jiang,
As you said that, there could be a problem with HTM (SpirMeOTAD).
Whenever you make devices, as early as possible you should go for I-V Characterization. One more important thing is that the way you are making devices affects the cell parameters.
FF, Voc and Jsc mainly depends on morphology of active material (TiO2) and sensitizer. The hicknesses of the layers also plays significant role to get better cell parameters.
You can follow these articles for better understanding and fabrication of devices.
1. http://pubs.acs.org/doi/abs/10.1021/ja809598r
2. http://www.nature.com/nature/journal/v499/n7458/full/nature12340.html
3. http://pubs.rsc.org/en/Content/ArticleLanding/2014/EE/c3ee43707h#!divAbstract
_Thanks,
Hi there,
Fill factor of an ideal solar cell is one. Nevertheless, in an actual cell made, fill factor is always less than one . Fill factor is increased to the product of Voc and Isc to find out the actual power delivered by cell. Less value of fill factor means that efficiency of the cell will be small. Fill factor may be less if series resistance will be high as voltage drop will occur across this resistance. To improve fill factor, one should select the material of low resistivity provided it follows all other requirements .i.e., optimum band gap around 1. 4 eV , low density of recombination centers, higher absorption coefficient and more built in potential.
Regards,
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