New efficiency record for perovskite–organic solar cells
Researchers from the National University of Singapore (NUS), in collaboration with The University of Hong Kong and Southern University of Science and Technology, say they have set a new record in the power conversion efficiency of solar cells made using perovskite and organic materials. Published in the journal Nature Energy, their breakthrough paves the way for flexible, lightweight, low-cost and ultrathin photovoltaic cells which are ideal for powering vehicles and other applications.
The conventional solar cells used in solar power plants are based on a single-junction architecture, and the practical power conversion efficiency of single-junction solar cells is limited to about 27% in industrial production. In order to raise the power conversion efficiency of solar cells to go beyond 30%, stacks of two or more absorber layers (multi-junction cells) are required. NUS Assistant Professor Hou Yi and his team thus looked to break new ground in the field of tandem solar cells, which are made using two different types of photovoltaic materials — in this case, perovskite and organic materials.
A tandem solar cell comprises two or more subcells electrically connected using interconnecting layers (ICLs). The ICL plays a critical role in determining the performance and reproducibility of a device. An effective ICL should be chemically inert, electrically conductive and optically transparent.
Although perovskite–organic tandem solar cells are attractive for next-generation thin-film photovoltaics, their efficiency lags behind other types of tandem solar cells. To address this technological challenge, Asst Prof Hou and his team developed a novel and effective ICL that reduces voltage, optical and electrical losses within the tandem solar cell. This innovation significantly improves the efficiency of the perovskite–organic tandem solar cells, achieving a power conversion rate of 23.6% — the best known performance for this type of solar cell to date.
The team’s achievement is a significant leap from the current power conversion rate of about 20% reported by other studies on perovskite–organic tandem solar cells, and is approaching the power conversion rate of 26.7% of silicon solar cells, which is the dominating solar technology in the current solar photovoltaic (PV) market. The discovery also opens the door to thin-film tandem solar cells that are light and bendable, which could have wide-ranging applications such as for solar-powered blinds, vehicles, boats and other mobile devices.
“Our study shows the great potential of perovskite-based tandem solar cells for future commercial application of photovoltaic technology,” Asst Prof Hou said. “Building on our new discovery, we hope to further improve the performance of our tandem solar cells and scale up this technology.”
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