The solar cell is constructed on a fluorine-doped tin oxide substrate coated with titanium dioxide, an electron selective layer made of mesoporous titanium dioxide, an insulating spacer layer of zirconium dioxide and a graphite electrode. The micro-module made with this battery passed the hot spot test for the first time.
A 10×10 cm2 perovskite solar module with carbon-based back contacts.
A group of scientists led by the Fraunhofer ISE in Germany tried to improve the stability of perovskite solar cells by using carbon-based electrodes. They claimed that these electrodes have a significant effect on the degradation caused by reverse bias. Excellent flexibility.
The researchers explained that the reverse bias behavior of perovskite solar cells was almost ignored by previous studies, although it affects long-term stability and prevents the device from reaching commercial maturity. "Defective or current mismatched photovoltaic cells can be regarded as the internal source of hot spots in the module, and the partial shading of the photovoltaic module during its operation is considered to be the external and frequent cause of degradation caused by reverse bias. , "they said. "In previous studies, applying a negative voltage to a traditional perovskite solar cell stack would cause device breakdown and irreversible damage."
The solar cell is built on a fluorine-doped tin oxide (FTO) substrate coated with titanium dioxide (c-TiO2), an electron selective layer made of mesoporous titanium dioxide (m-TiO2), a zirconium dioxide (ZrO2) insulating spacer layer and graphite electrodes . "Carbon-based electrodes are not easy to melt at high temperatures, (metal) ions will not migrate from the electrode to the perovskite absorber, nor will they be oxidized, which makes them ideal for improving the stability of perovskite solar cells," the scientists emphasize.
Through dark IV measurement, they found that the breakdown voltage of the battery is about -3.6 V, however, the device will only degrade when the reverse bias exceeds -9 V. The research team specifically identified two different degradation mechanisms related to reverse bias: iodine loss due to hole tunneling into the perovskite, which occurs under low reverse bias, and The perovskite in the battery can only be decomposed after a long time; the formation of lead (II) iodide (PbI2), which is caused by local heating during a large reverse bias, and causes a shunting effect.
These cells are then used to manufacture a 10×10 cm2 perovskite solar module with carbon-based back contacts. According to the IEC 61215:2016 international standard, its reverse bias behavior is analyzed through hot spot testing. The researchers affirmed that: "Passing this accelerated test for the first time confirms the excellent stability of the perovskite photovoltaic device and highlights its huge industrialization potential." "
Their research results were published in the paper Perovskite Photovoltaic Devices with Carbon-Based Electrosetting Reverse-Bias Voltages up to –9 V and Surpassing IEC 61215:2016 International Standard published on RRL Solar.
The research team also includes scholars from the National Renewable Energy Laboratory (NREL) of the US Department of Energy, the Swiss technology company Solaronix SA, and the Freiburg Materials Research Center (FMF) at the University of Freiburg.
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More articles from Emiliano Bellini
Wouldn't the problem be solved by placing a silicon diode that is normally reverse-biased on each cell?
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