A group of scientists, led by Prof. Yiqiang Zhan from Fudan University, has reported high-efficiency flexible perovskite solar cells (f-PSCs) by annealing a SnO2 ETL in a rough vacuum at a low temperature (100 ℃), and peak efficiency reached 20.14%.

SnO2 layers that have been prepared by this method have shown higher robustness and hydrophobicity in comparison with samples prepared in an air atmosphere and temperatures of 100 °C, leading to an improved ETL/perovskite interface connection and reducing defects in the SnO2/perovskite interface. The appropriate density of oxygen vacancies on the surface during this treatment can be responsible for higher conductivity, which is beneficial for charge transfer.

This work suggests that, in addition to high-temperature annealing, the control of oxygen partial pressure is also effective in achieving high conductivity for metal oxides even at low temperatures, which is meaningful for flexible electronics.

When utilizing a vacuum-assisted annealing method in SnO2 electron transport layer fabrication at a low temperature (100 ℃), a remarkable open circuit voltage (1.14 V) and efficiency (20.14%) were reported for PSCs with polyethylene terephthalate flexible substrates.

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