Inverted perovskite solar cell hits 21.4% efficiency with Ruddlesden-Popper passivation layer

South Korean scientists have used a vertically oriented passivation layer, featuring two-dimensional Ruddlesden-Popper perovskites (RPP), to mitigate nonradiative recombination in inverted perovskite solar cells. They achieved the highest efficiency ever reported for a perovskite cell formed by vacuum deposition.

Researchers at South Korea’s Ulsan National Institute of Science and Technology (UNIST) have developed an inverted perovskite solar cell with a vertically oriented passivation layer. It relies on two-dimensional Ruddlesden–Popper perovskites (RPP), which are known for their excellent stability.

The scientists said they were able to achieve a “highly ordered” passivation layer by gauging the deposition rate of the RP phase perovskite, which has a direct influence on its crystallographic orientation.

“We demonstrate the use of a highly oriented butylammonium RP perovskite as a surface passivation layer with bottom-up growth on the bulk perovskite absorber layer via vacuum deposition,” they explained. “In this process, the crystal formation time directly affects the crystallographic orientation of the passivation layer.”

They built the cell with an indium tin oxide (ITO) substrate, a hole transport layer (HTL) made of poly-triarylamine (PTAA), methylammonium lead iodide (MAPbI3) perovskite layer, the RPP passivation layer, an electron acceptor made of phenyl-C61-butyric acid methyl ester (PCBM), a zinc-oxide (ZnO) layer, and a silver (Ag) metal contact.

They said the 2D perovskite layer passivates the bulk perovskite defects and promotes charge transport efficiency. The champion cell designed with this configuration achieved a power conversion efficiency of 21.4%, which the academics described as the highest ever achieved for perovskite solar cells formed by vacuum deposition.

They described the cell in “A vertically oriented two-dimensional Ruddlesden–Popper phase perovskite passivation layer for efficient and stable inverted perovskite solar cells,” which was recently published in Energy & Environmental Science.

“Our findings provide a new perspective toward further improving the performance of perovskite solar cells by mitigating nonradiative recombination pathways in perovskites,” they said.

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