A research team led by Hamad Bin Khalifa University (HBKU) in Qatar has developed a perovskite solar cell that uses an electron transport layer (ETL) based on tin(IV) oxide (SnO2). They say it could improve electron mobility in the device.
The scientists said in “Moderate temperature deposition of RF magnetron sputtered SnO2-based electron transporting layer for triple cation perovskite solar cells” that perovskite solar devices often use titanium oxide (TiO2 i) as the primary contributor to the light-induced degradation observed in perovskite solar cells.
“Unlike TiO2 material, SnO2 can be processed at much lower temperatures using different deposition technologies, including solution processes, electrodeposition, electron-beam, atomic layer deposition and magnetron sputtering,” the researchers said. “Among all these thin fabrication methods, magnetron sputtering (MS) is one of the most promising technologies due to its advantages related to cost-effectiveness and uniform large-scale SnO2 thin films.”
The research group sputtered the SnO2 material through high-energy argon-plasma ions on a substrate made of fluorine-doped tin oxide (FTO) and glass. The cell also utilizes an absorber made of a perovskite material known as Cs0.05MA0.10FA0.85Pb(I0.85Br0.15)3, a hole transporting layer (HTL) made of Spiro-OMeTAD, and a top electrode based on gold (Au).
The scientists said the SnO2 thin film showed high crystalline quality, as it incorporates more oxygen due to an air-thermal-annealing treatment.
“The SnO2 films have shown rather a high optical transmittance in the visible range which is higher than 80%,” they said. “The thermal annealing process has clearly enhanced the electrical conductivity by significantly increasing the electron mobility and this finding is matching with the increase in crystallite size after the annealing process.”
They compared the performance of the device with that of a reference cell with an ETL based on SnO2 deposited without the thermal annealing process. The latter achieved a power conversion efficiency of 15.07% and the former of 17.1%. The new cell also achieved an open-circuit voltage of 1.045 V, a short-circuit current of 22.01 mA/cm2, and a fill factor of 74.3%, while showing an average operational lifetime over 200 h.
“Sputtered SnO2 as ETL was demonstrated to enable a good PV device performance, stability and lifetime and could serve as a promising route for further development and integration of sputtered SnO2 films into large-scale and cost-effective perovskite PV modules,” the research group concluded.
*The article was updated to reflect that the Hamad Bin Khalifa University (HBKU) is based in Qatar, and not in Iraq, as we previously reported.
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