Potassium improves perovskite solar cells, researchers find

Potassium could enhance the efficiency of perovskite-based solar cells, according to an international team of researchers, led by the University of Cambridge.

The researchers found that the addition of potassium iodide "heals" defects in the crystalline structure of perovskites, causing electrons to move more freely and hence improving the conversion efficiency of the material. In addition, adding potassium iodide to perovskite inks immobilises ion movement, which makes the material more stable at the desired bandgap.

"Potassium stabilises the perovskite bandgaps we want for tandem solar cells and makes them more luminescent, which means more efficient solar cells," Sam Stranks from Cambridge’s Cavendish Laboratory, who led the research, said in an announcement, published Wednesday.

According to the announcement, the perovskite and potassium devices demonstrated good stability in tests and 21.5% efficiency in converting light into electricity, which is similar to the best perovskite-based solar cells.

Perovskites could be used as an efficiency-boosting layer for silicon solar cells, or stand-alone solar cells or coloured LEDs. Their first widespread use will probably be silicon tandem solar cells, says the announcement.

Tandem cells made of two perovskite layers with ideal bandgaps have a theoretical efficiency limit of 45% and a practical limit of 35%, which is above the current practical efficiency limits for silicon, the researchers note.

The study, published in journal Nature, used solar cells based on metal halide perovskites.

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