Methylammonium-free perovskite solar cell with 22.29% efficiency


Researchers from Japan's National Institute for Materials Science (NIMS) have fabricated a solar cell based on a perovskite material that doesn't contain methylammonium (MA) molecules. These molecules have intrinsic thermal instability and contribute to increasing the typical thermal instability of perovskite PV devices.

The scientists used pentafluorophenylhydrazine (5F-PHZ) instead of MA for the interfacial passivation of the 3D HaP perovskite layer and built a cell with a p-i-n device structure and an area of 1 cm2.

The device relies on an indium tin oxide (ITO) substrate, a hole transport layer based on nickel(II) oxide (NiOx), the perovskite layer, a layer made of [2-(3,6-Dimethoxy-9H-carbazol-9-yl)ethyl]phosphonic acid, which is also known as MeO-2PACz, an electron transport layer made of buckminsterfullerene (C60), and a silver (Ag) metal contact.

Tested under standard illumination conditions, the device achieved a power conversion efficiency of 22.29%, an open-circuit voltage of 1.178 V, a short-circuit current of 24.51 mAcm−2, and a fill factor of 77.2%. A reference cell without the 5F-PHZ treatment achieved an efficiency of 18.10%, an open-circuit voltage of 1.096 V, a short-circuit current of 22.88 mAcm−2, and a fill factor of 72.2%.

“This improvement in efficiency is obtained with a small open-circuit voltage deficit of 0.338 V,” the scientists said. “Considering the little difference between the bandgaps of the control and 5F-PHZ treated HaP films, the open-circuit voltage enhancement is attributed to the reduction of non-radiative recombination.”

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The solar cell was also able to retain around 92.52% of its initial efficiency after 500 h. The same device without the 5F-PHZ treatment was able to retain only 73.5%. “These results indicate that the device with 5F-PHZ treatment significantly improves the thermal stability which is benefited by interfacial halogen bonding modulation,” the academics stated.

They introduced the cell technology in “Interfacial Embedding for High-Efficiency and Stable Methylammonium-Free Perovskite Solar Cells with Fluoroarene Hydrazine,” which was recently published in Advanced Energy Materials.

“We would like to develop our techniques with Japanese companies such as Sekisui, Toshiba,  Aisin,  Kaneka, and EneCoat Technologies,” researcher Dhruba B. Khadka told pv magazine.

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