I have fabricated Perovskite solar cells using
ITO/PEDOT: PSS (~50nm)/perovskite(~300nm)/PCBM(~30nm)/Ag.
The device IV results shows that the Jsc is very low (~3mA/cm2) and Voc~0.8V.
I have a doubt in the PEDOT: PSS layer thickness, because in many reports, the thickness shown are different.
Therefore, please suggest me about PEDOT: PSS layer thickness and if anything else to care about.
Thanks
Hi, Pilik,
Firstly, please be aware of that PEDOT:PSS water dispersion solution has different types of grades. Commercially available grades are various. Please see www.heraeus.com website regarding the type of PEDOT:PSS solution used for solar cells.
Secondly, the processing PEDOT:PSS thin films from solution is crucial to the device performance such as drying temperature, film quality and film thickness. I suggest that you should do your own study to optimise the processing conditions. The recommended annealing temperature is 120 degree C for 10 to 30 mins. The quality of thin films from solution processing very much depends on so much factors. Lab temperature and humidity should also be taken care of.
Some dopants such as IPA could help get better film quality.
Although device performance can also rely on other factors, once you optimise the hole injection layer. I am sure you will get the device performance what most researchers reported. Best luck!
Dear Pilik,
welcome,
I think your question was asked more than once in the research gate. If you search you can find some useful answer. Here i will give a conceptual answer which may be applied for any layer of the thin film technology.
It is so the very thin film like PEDOT:PSS must be homogeneous both in thickness and coverage of the substrate. Solution processed very thin film may have pinholes in the sense it does not cover totally the substrate. In addition to thickness nonhomogeneity. But the most serious factor is the pinholes. It is advisable to microscopically investigate the layer and optimize its deposition condition to achieve the required characteristics.
Iagree with Xuhua that every laboratory has its environment which may be different from that in the other laboratories.
From the theoretical point of view the PEDOT:PSS layer must be as thin as possible as it has very low mobility. This is a characteristics of organic materials.
But as you reduce the thickness the formation of the pin holes may increase appreciable. So you have to compromise the the thickness to satisfy the two requirements.
Best wishes
Thanks Dear Wang, for your kind suggestions.
I have been using CLEVIOS P VP AI 4083(PEDOT:PSS) as HTL in pristine form with out any dopants by annealing at 120 degrreC for 20 mins.
Dear Zekry,
Thanks for your inputs. I have taken care of the homogeneity and there was no such pin holes seen in AFM images. May be it needs optimization in thickness wise.
Dear Pilik,
Other important factor affecting the behavior of the PEDOT:PSS is its sensitivity to moisture content in the environment in addition to temperature and pressure.
Please for the details of the effects please see for example: https://worldwidescience.org/topicpages/p/pedot+pss+film.html
So, there are trials that such organic hole transport layer is substituted by a metallic hole transport layer which much less sensitive to environmental effects.
So, the matter could be other effects than the thickness itself.
Best wishes
Dear Pilik,
You have to optimize each layer of perovskite solar cells. Not only CTLs but absorber materials are also responsible for device performance. One more thing, PEDOT:PSS is hygroscopic in nature and absorbs moisture from surroundings thus degrades absorber material. Due to this reason device stability decreases. You can use metal oxide materials instead of PEDOT:PSS as HTL (e.g. CuO, NiOx etc.); this selection will enhance the overall performance of perovskite based solar cells and also will reduce fabrication cost.
Good Luck!
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