The Korea Energy Research Institute has significantly improved semi-transparent perovskite solar cell technology, achieving a world-leading efficiency of 21.68% and demonstrating exceptional durability. This breakthrough, aimed at expanding the application of solar cells in windows and tandem configurations, addresses key challenges in achieving carbon neutrality by 2050. Through innovative research, the team has made a significant contribution to the field of solar energy by improving the stability and efficiency of these cells. energy. Credit: Korea Institute of Energy Research
The problem of metal oxide layer degradation in semi-transparent perovskite solar cells has been successfully solved, showing significant progress for the first time in the world.
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The Photovoltaic Research Division of the Korea Energy Research Institute, in collaboration with the KIER Energy AI and Computational Science Laboratory, has made progress in improving the durability and efficiency of semi-transparent perovskite solar cells. These cells hold promise for applications in building windows and developing tandem solar cells.
The translucent solar cells achieved a record efficiency of 21.68%, making them the most efficient perovskite solar cells using transparent electrodes in the world. In addition, they exhibited excellent durability, with more than 99% of their initial efficiency retained after 240 hours of operation.
The quest for carbon neutrality and solar innovation
Key to achieving carbon neutrality by 2050 is achieving “ultra-high efficiency” and “diversification of applications” of next-generation solar cell technology, overcoming limitations in installation locations and national land area. This requires efficient and multifunctional technologies such as tandem solar cells and solar cells for windows. Both technologies require highly efficient and stable semi-transparent perovskite solar cells.
To produce translucent perovskite solar cells, it is necessary to replace the metal electrodes of conventional opaque solar cells with transparent electrodes that allow light to pass through. During this process, high-energy particles are generated, which leads to the deterioration of the performance of the hole transport layer.
Perovskite solar cell, semi-transparent perovskite solar cell, perovskite tandem solar cell from left. Credit: Korea Institute of Energy Research
To prevent this, it is common to place a metal oxide layer between the hole transport layer and the transparent electrode layer to act as a buffer. However, compared to opaque solar cells produced under the same conditions, the charge-carrying properties and stability of semi-transparent devices are reduced, the exact reasons and solutions for this have not been elucidated.
Progress in Understanding and Improving Solar Cell Stability
The researchers used electro-optical analysis and atomic-level computational science to determine the causes of the reduced charge-transport properties and stability that occur during the fabrication of semi-transparent perovskite solar cells. Through this, they discovered that lithium ions (Li), added to increase the electrical conductivity of the hole-carrying layer, diffuse into the metal oxide buffer layer, which eventually alters the metal oxide buffer layer’s electronic structure. its characteristics.
Furthermore, in addition to identifying the cause, the researchers solved the problem by optimizing the oxidation time of the hole transport layer. They found that conversion of lithium ions to stable lithium oxide (LixOy) through optimized oxidation reduces lithium ion diffusion, thereby increasing device stability. This discovery reveals that lithium oxide, previously considered a simple reaction product, can play an important role in increasing efficiency and stability.
From left, Ahn SeJin, Ahn Seung-kyu, Yim Kanghoon and Naqvi Syed Dildar Haider in the circle. Credit: Korea Institute of Energy Research
The developed process resulted in semi-transparent perovskite solar cells with an impressive 21.68% efficiency, the highest among all transparent-electrode perovskite solar cells. In addition, this study demonstrated its superior efficacy and stability by demonstrating an impressive retention of more than 99% of its initial efficiency under 400 hours of dark storage and over 240 hours of continuous illuminated operation.
Application in Bifacial Tandem Solar Cells
The research team went further and applied the fabricated solar cells as the top cell of tandem solar cells, creating the country’s first double-faced tandem solar cells, using light reflected from the back as well as incident from the front surface. Jusung Engineering Co., Ltd. and in collaboration with the German Jülich Research Center, bifacial tandem solar cells have achieved high bifacial equivalent efficiencies: 31.5% for four-terminal and 26.4% for two-terminal configurations. background was 20% of standard sunlight.
Head of the research, Dr. from Photovoltaic Research Department. Ahn SeJin said, “This research is a significant advance in this field by investigating the degradation process that occurs at the interface of an organic compound and a metal oxide buffer layer. semi-transparent perovskite solar cells” and added: “Our solution is easily implemented and shows great potential for future use of the technologies we have developed.”
Reference: Syed Dildar Haider Naqvi, Kyungnan Son, Wonzee Jung, Hui ung Hwang, Sangmin Lee, Arheum Kim Sunwo, Arheum Kim Sunwo, “Reducing Internal Interfacial Degradation for High Efficiency and Long-Term Stability in Translucent Perovskite Solar Cells”, Jeong Won Kim, Min Gu Kang, Hee-eun Song, Sungjun Hong, Inyoung Jeong, Seungkyu Ahn, Andreas Lambertz, Kaining Ding, Weiyuan Duan, Kanghoon Yim, and SeJin Ahn, 30 Oct 2023, Advanced Energy Materials.
DOI: 10.1002/aenm.202302147