NREL Technique Leads to Improved Perovskite Solar Cells

Researchers at the US Energy Department’s National Renewable Energy Laboratory (NREL) have developed a new method to increase the efficiency of perovskite solar cells.

The research, which was carried out in collaboration with researchers at Shanghai Jiao Tong University (SJTU), has found a way to make perovskite solar cells more efficient and reliable with higher reproducibility.

The program received funding under the US Department of Energy SunShot Initiative, which was launched in 2011.

NREL scientists revealed that treating hybrid halide perovskite solar cells with a specific solution of methyl ammonium bromide (MABr) would repair defects like noncontinuous crystals and nonuniform crystals formed during their manufacture.

They converted a low-quality perovskite film with pinholes and small grains into a high-quality film without pinholes and with large grains.

The technique resulted in improving the efficiency of perovskite film to convert sunlight into electricity to 19%.

The efficiency of perovskites has increased to 22% currently, compared to 4% in 2009, when tests were conducted for the first time.

But the efficiency can vary to somewhere between 15% and 20% depending on the skills of the researchers making perovskites.

 NREL researchers have identified that lack of enough time to properly add the anti-solvent while preparing Perovskite films could result in perovskite crystals with defects.

The defects can significantly reduce the effectiveness of a perovskite cell.

To address the issue, the scientists from NREL and SJTU developed a new method, using the Ostwald ripening process.

The process involves small crystals dissolving and then redepositing onto larger crystals.

The researchers noted: “With the Ostwald ripening process, different-sized nanocrystals formed with different film qualities could then grow into pinhole-free perovskite films with similar large crystal sizes.

 “Thus, this new chemical approach enhances processing tolerance to the initial perovskite film quality and improves the reproducibility of device fabrication.”

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