Within the first second or two of illumination/measurement, the Jsc ~15-20 mA/cm^2, but quickly drops to ~5 mA/cm^2. This is observable using both a keithley sweeping through voltages to generate an IV curve and just measuring short circuit current with a multimeter. Voltages are stable.
The configuration of our solar cell is: ITO/TiO2-bl/perovskite/Spiro-Ometad/Au, all material is deposited via spin-coating except for the gold which is ebeam evaporated(100 nm).
Dear Trent,
Similar question was asked before on the research gate about the short stability of organic solar cells and i gave an answer there together with some useful contributions from other colleagues. Since the perovskite solar cells are hybrid organometalic cells,
they are subjected to short term instability because the changes occurring in the materials because of the UV light, heat and the presence of moisture and oxygen.
Such degradation is one of the main challenges for the commercialization of such type of cells. Please fore more information please follow the link:https://www.researchgate.net/post/Why_do_we_observe_different_values_of_PCE_when_we_repeat_the_measruments_on_the_same_device_in_BHJ-Oraganic_solar_cells
wish you success.
Thank you for your prompt reply!
I'm aware of the stability issues associated with perovskites, and have first-hand observed the degradation of perovskite back to PbI2 under illumination, but I think my current issue is slightly different (though these cells do degrade over time as well). Each subsequent measurement begins back where the first one did, making the degradation "reproducible." In addition, the change is so abrupt it happens within a 3-5 second measurement. Attached is the resulting IV curve showing the drop in real-time (voltage is swept from 0->1.1V). Waiting a few seconds and doing the measurement again results in the same Isc.
c-TiO2 and HTM of your devices have problem. Measure the resistance of c-TiO2 layer and report it here.
Thanks for your quick reply!
My c-TiO2 layer on glass is ~400 kohm; 4-probe measurement is too high.
My previous measurement was just on glass to ensure it wasn't affected by the ITO. Measuring the resistance of ITO/c-TiO2 yields around 200 ohms.
Thank you again for your look at this problem, its greatly appreciated!
Very interesting!
Sorry Trent, it is not short term stability issue as your curves are reproachable from measurement to the other.What do you have is the so called S-curve phenomenon of the solar cell. Such shape of curve is normally observed when the ETL and the HTL interfaces to the active perovskite layer are nonohmic and have nonlinear properties.
I observed this phenomenon and explained it in silicon solar cells for long time. The same happens with the perovskite solar cells. You have to be sure that your transport layer build interfaces that behave low ohmic. For more information about this phenomenon please return to the paper in the link:
https://www.researchgate.net/publication/232710923_A._Zekry_and_G._ElDllal__effect_of_MS_contact_on_the_electrical_behavior_of_solar_cells_Journal_of_solid-state_Electronics_Vol.31_No.1_1988.
Article A. Zekry and G. El-Dllal, “ effect of MS contact on the elec...
What method did you use for c-TiO2 deposition? 200 Ohm is very low for c-TiO2 and the reason for getting such bad IV curve. I had the same issue. Try to make a pinhole free c-TiO2 layer with resistance of at least a few KOhms. Then you will get better results. Also take care of HTM layer & make sure you deposit a layer with a thickness of at least 200nm.
Our previous experiments were using TTIP in IPA (0.15M), but we've since switched to TTIP in IPA w/ nitric acid. These solutions are spin coated at 6k rpm after washing/plasma cleaning our ITO. They are then heated to 450 C for half an hour.
Thank you so much for your assistance, I'm working to reproduce your advice now.
- Badges
- Science topic