Professor Kwanghee Lee's research team has developed an organic nanocomposite structure to enhance the reliability of perovskite solar cells

□ Professor Kwanghee Lee of the School of Materials Science and Engineering at the Gwangju Institute of Science and Technoloogy (GIST) has succeeded in developing an organic nanocomposite structure to enhance the reliability of perovskite solar cells.

* Perovskite solar cell: A solar cell that uses perovskite crystalline organic / inorganic composite ionic crystalline material as a photoactive layer.

□ Titanium oxide (TiO2), which is most commonly used as an electron transport layer for perovskite solar cells, cannot be easily applied to plastic substrates or flexible transparent electrodes due to the process temperature approaching 500 °C, and it also suffers from performance degradation. These drawbacks hamper the practical development of perovskite solar cells fabricated via a printing process on flexible plastic substrates.

∘ In particular, titanium oxide-based perovskite solar cells have a hysteresis phenomenon that varies greatly depending on the scan direction and the speed of the current-voltage curve, and thus a reliable performance evaluation is not possible.

* Hysteresis: a phenomenon in which the physical characteristics of a substance is determined by the history of changed states that the substance has experienced. Generally, perovskite solar cells measured under quick scanning conditions, significant hysteresis can be present in the current−voltage curves.

□ The research team developed an innovative method to fabricate low-temperature-processed, hysteresis-free, and efficiently reliable perovskite solar cells with a regular structure by introducing self-assembled organic nanocomposites (SAONs) as a new electron transport layer that employs n-type polyelectrolytes and fullerene derivatives.

∘ By using a spontaneous vertical phase separation driven by the surface energy difference of the SAON components, the researchers succeeded in forming ideal, self-organized electron transport layers with dual functionality as an electron acceptor and surface work function modifier.

∘ In particular, the researchers discovered that the hysteresis phenomenon, which has been a problem in existing titanium oxide materials, was completely removed, and a highly reliable perovskite solar cell can be manufactured by using this organic nanocomposite process.

□ Professor Kwanghee Lee said, "This research will contribute to the development of highly reliable perovskite solar cells suitable for commercial applications and will also provide scientific and technological inspiration to the organic–inorganic hybrid electronics fields by developing organic nanocomposites that will replace the use of titanium oxide, which has serious limitations."

□ This research, which was supported by the R&D program of MSIP/COMPA, the National Research Foundation of Korea (NRF), and by the Ministry of Science, ICT and Future Planning. "A Printable Organic Electron Transport Layer for Low-Temperature-Processed, Hysteresis-Free, and Stable Planar Perovskite Solar Cells" was authored by Jinho Lee, Junghwan Kim, Chang-Lyoul Lee, Geunjin Kim, Tae Kyun Kim, Hyungcheol Back, Suhyun Jung, Kilho Yu, Soonil Hong, Seongyu Lee, Seok Kim, Soyeong Jeong, Hongkyu Kang, and Kwanghee Lee and was published on April 20, 2017, in Advanced Energy Materials.