GIST Research Team Proposes Method to Improve Performance of Perovskite Solar Cells

[Asia Economy Honam Reporting Headquarters Reporter Lee Gwan-woo] Gwangju Institute of Science and Technology (GIST) announced on the 28th that a research team led by Professor Kwanghee Lee of the Department of Materials Science and Engineering and Professor Heeju Kim of the Convergence Technology Department found a way to improve the efficiency of perovskite solar cells by utilizing ions in which cations and anions coexist within a single molecule.

The research team confirmed that the performance of perovskite solar cells can be enhanced by passivating internal defects of organic-inorganic hybrid perovskites through the addition of zwitterion additives.

Organic-inorganic hybrid perovskite solar cells are attracting attention as next-generation solar cells due to their solution processability, thin and lightweight characteristics, and high device efficiency exceeding 25%.

However, there is a problem of device performance degradation caused by defects inherent in the organic-inorganic hybrid perovskite material itself, making defect control essential for producing high-performance perovskite solar cells.

Defects inside perovskite materials carry charges, which are broadly divided into positive electric charges and negative electric charges.

To control these, methods using materials with a single charge or lone electron pairs for passivation are widely known, but they are limited to passivating only one type of charge.

The research team focused on amino acids, representative zwitterions in which cations and anions coexist simultaneously within a single molecule, and among them used L-alanine, which is simple and similar to the perovskite material precursor.

By using L-alanine as an additive to the perovskite material, they confirmed defect passivation inside the material and an increase in grain size, and also discovered that the solar cell device efficiency increased from the existing 18.3% to 20.3%.

They verified that this improvement in device efficiency was due to the suppression of nonradiative recombination in the perovskite material through photoluminescence spectroscopy and time-resolved single-photon counting techniques, with photoluminescence lifetime increasing more than tenfold.

Additionally, internal defect reduction was measured through space-charge-limited current measurements, and conductivity analysis at low temperatures confirmed that the zwitterions inhibit ion migration inside the perovskite.

Professor Kwanghee Lee said, “This research achievement presents a new principle that can solve the internal defect problem of organic-inorganic hybrid perovskite materials, which must be addressed in the development of next-generation solar cells, using a simple single zwitterion molecule.” He added, “This is expected to be applicable not only in the solar cell field but also in various semiconductor devices using organic-inorganic hybrid perovskites, such as light-emitting diodes, transistors, and photodetectors.”

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