I have an electrode design where I would like to use C60/Ti as an n-type electrode in perovskite solar devices.
But when heated, the performance of devices using this electrode falls.
Any ideas on how to keep the same material set but modify it in some way to improve thermal stability?
@Ioannis Samaras
We surprisingly find that the performance drops when heated in both inert and air. Heating at temps as low as 80-110 deg for 1 hour, we find the performance of our PV devices is much lower. Every other material and interface we are using has proven to be thermally stable aside from c60/titanium.
Maybe there is some interaction[1] of the C60, or a possible (molecular ?) intercalation[2], with the next layer. An intercalation process scales with the heating time, and it's kinetics scales with the Temperature[3]. So, maybe you are interested to start benchmark tests under reducing, initially, the parameter of the heating time (
Thank you Ioannis. We will certainly try time and temperature variations. I will post here what our rough conclusions are when we have collected more data.
I think molecular intercalation or metal ion diffusion is certainly a possibility.
So far we have crudely retarded the degradation by implementing a SnO2 metal oxide layer between the Titanium and the C60. After introducing Ti/SnO2/C60 we now see thermal stability up to 80oC but not in a excess of 110oC (for 1 hour).
However I am hesitant to describe this as 'solving' the issue because I believe there is an active interaction between C60 and Titanium that may still occur over time within the operational temperature of a solar cell.
Regardless, I think another issue that may tie into our thermal instability is that the quality (roughness, low density, low sheet conductivity) of our titanium layers is relatively poor. Ideally we would have a dense, uniform and smooth titanium layer on which to build a planarizing passivating guard layer (E.g SnO2 - which also is a n-type electron selector) and our final n-type material (E.g C60).
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