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Black perovksite solar cell achieves 20.25% efficiency

The Chinese Academy of Sciences has developed a black perovskite solar cell that reportedly achieved the the highest efficiency ever reported for PV devices built with this perovskite material and a dopant-free hole transport layer based on the P3HT polymer. The cell was also able to retain around 93% of its original efficiency after continuous illumination for 570 h.

The Chinese Academy of Sciences (CAS) has announced that a group of its researchers has fabricated a solar cell based on cesium-lead iodide (CsPbI3) perovskite, which is also known as black perovskite.

This CsPbI3 is being tested in PV devices as it promises to offer superior moisture and illumination stability. This perovskite material has an energy bandgap of approximately 1.7 eV and, according to several scientists, is an ideal solution for single-junction and wide-band-gap sub-cells in tandem PV devices.

“We developed a new approach for CsPbI3 solar cells that opens new opportunities for constructing all-inorganic perovskite solar modules,” the research’s lead author, Jin-Song Hu, told pv magazine.

The scientists utilized a hydrogen-bonding-facilitated strategy to extract dimethylammonium (DMA) from the black perovskite absorber, which may result in local heterogeneity, defect formation, and rough morphology – all factors that could be detrimental to the cell efficiency and stability.

The strategy consists of bonding DMA with polyacrylic acid (PAA) during the formation of the CsPbI3 film, a process that would favor DMA extraction via the newly formed hydrogen bonds.

“The PAA-added sample exhibited relatively faster phase transformation and achieved the high-quality CsPbI3 film with no DMA residue,” the scientists said. “Systematic experimental and theoretical investigations revealed that the hydrogen bonding facilitated the DMA extraction by lowering its escaping energy barrier.”

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The group built the cell with a substrate made of fluorine-doped tin oxide (FTO), a titanium dioxide (TiO2) electron transfer layer (ETL), the CsPbI3 absorber, a hole transport layer (HTL) relying on a regioregular poly (3-hexylthiophene) (P3HT) polymer, and a gold (AU) metal contact.

Tested under standard illumination conditions, this device achieved a power conversion efficiency of 20.25%, which the scientists said is the highest efficiency reported on CsPbI3 PSCs with a dopant-free P3HT HTL.

“The device demonstrated superior moisture and operational stability in terms of maintaining 94% of their initial efficiency after aging at low relative humidity (RH) conditions for 10,224 h and over 93% efficiency after continuous illumination for 570 h,” they explained.

They described the novel cell technology and the related manufacturing process in the study “Hydrogen-bonding-facilitated dimethylammonium extraction for stable and efficient CsPbI3 solar cells with environmentally benign processing,” published in Joule.

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Source: pv magazine