| Work Detail |
The result has been confirmed by the U.S. Department of Energys National Renewable Energy Laboratory (NREL). Chinese solar module manufacturer Longi has revealed that it has achieved a power conversion efficiency of 34.85% for a dual-terminal tandem perovskite solar cell. The U.S. Department of Energys National Renewable Energy Laboratory (NREL) certified the result, which represents a world record for this type of cell. The previous record was held by Longi itself, which achieved an efficiency of 34.6% for a device with the same configuration in September, when the manufacturer published a scientific paper detailing the cell design, which was originally unveiled in November 2023. Longis result is also the first certified efficiency known to exceed the Shockley-Queisser limit of 33.7% for a double-junction tandem solar cell. In September, Longis research team explained that the cell is based on a bilayer interface passivation strategy that reportedly maximizes both electron transport and hole blocking. This is achieved through the incorporation of a thin layer of lithium fluoride (LiF) and the deposition of short-chain ethylene diammonium dioxide (EDAI) molecules. “A thicker LiF layer can help improve passivation, but it comes with a significant, undesirable resistive loss,” the researchers wrote at the time. “However, the EDAI molecule can chemically passivate the unpassivated regions not in contact with the LiF layer, forming localized nanoscale contacts at the perovskite/C60 interface, which can provide an optimal balance between passivation and charge extraction.” The researchers added that they achieved better structural coupling between the top perovskite cell and the bottom crystalline silicon cell thanks to a patented technology for silicon heterojunction solar cells with an asymmetric textured surface. The front surface of this silicon cell has a finely textured surface, which facilitates the solution preparation of the perovskite film, while the back surface of the silicon cell uses a standard large-scale textured surface to achieve better passivation and infrared spectral response, they stated. The LiF/EDAI bilayer enabled increased open-circuit voltage and fill factor of the device to 1.97 V and 83.0%, respectively, by suppressing interfacial recombination along with more efficient charge extraction at the electron transport layer (ETL) interface. The research work received strong support from Suzhou University, Huaneng Clean Energy Research Institute and The Hong Kong Polytechnic University (HKPU). |
