Main content:
In recent years, the potential of perovskite materials in the photovoltaic industry has been continuously explored, and the efficiency of single-junction perovskite solar cells has repeatedly reached a new high. In order to further improve the photoelectric conversion efficiency, Li Yongfang and Meng Lei's team from the Institute of Chemistry of the Chinese Academy of Sciences and the National Research Center for Molecular Sciences in Beijing collaborated with Professor Felix Lang from the University of Potsdam in Germany. Wide-band gap perovskite solar cells with open circuit voltage of 1.36V and photoelectric conversion efficiency (power conversion system) of more than 18% were realized (the improvement of open circuit voltage is a key factor to improve the efficiency of perovskite and organic stack solar cells).
Efficient structure of perovskite-organic laminated solar cells
The team has made an important breakthrough in the field of photovoltaic technology by combining a wide-band gap perovskite solar cell with an organic solar cell to build an innovative perovskite-organic laminated solar cell. This new type of laminated solar cell shows an impressive photoelectric conversion efficiency of 26.4%. This result represents the highest efficiency of this type of laminated solar cell to date and marks another leap forward in photovoltaic technology.
The core of this research is how to improve the photoelectric conversion efficiency of perovskite materials by reducing voltage loss. By combining wide-band gap perovskite materials with organic materials in a laminated structure, the research team greatly expanded the range of available solar spectra.
The explanation for wide-band gap perovskite materials is that they are used to absorb short-wavelength sunlight, while organic materials focus on absorbing near-infrared long-wavelength sunlight, and such structural design not only reduces energy loss, but also improves the overall photoelectric efficiency. This achievement provides a new solution to help solve the voltage loss of perovskite materials in solar cells, and has important guiding significance for the development of perovskite and organic stacked solar cells in the future.
It is worth mentioning that laminated solar cells have great potential in practical applications. Through the laminated structure, the perovskite cell can effectively filter high-energy photons, thereby protecting the organic layer from degradation under long-term light.
At the same time, the organic layer can also provide a certain encapsulation effect, which significantly improves the stability of the battery due to the effective isolation of water and oxygen intrusion. These design improvements make perovskite-organic stacked solar cells superior to single-junction perovskite and single-junction organic solar cells, especially in terms of performance, durability and efficiency, which opens up new directions for the development of future solar photovoltaic systems.
Multiple advantages of perovskite/organic laminated solar cells
According to the official introduction, compared with other types of laminated solar cells, perovskite/organic laminated solar cells have attracted much attention as an emerging technology. In perovskite/organic layered solar cells, wide-band gap perovskite material is used as the top cell to absorb short-wavelength sunlight, and narrow band gap organic active layer is used as the bottom cell to absorb near-red wavelength sunlight, which greatly broadens the available solar spectral range and reduces energy loss.
At the same time, perovskite cells can filter high-energy photons to protect the organic active layer and prevent its photodegradation. The organic cell can be used as an encapsulation layer to insulate water oxygen and improve environmental stability, while the middle transparent electrode layer of the laminated solar cell can also alleviate the ion diffusion problem at the negative electrode of the perovskite top battery, so that the stability of the perovskite-organic laminated solar cell is better than that of the single junction perovskite and single junction organic solar cell. In addition, perovskite/organic laminated solar cells also retain the intrinsic advantages of solution-ready solar cells.
Passivation strategy solves interface recombination and voltage loss
In perovskite solar cells, there is often a serious interfacial recombination at the interface between the wide-band gap perovskite absorption layer and the C60 electron transport layer, and the surface-state-induced Fermi level pinning effect will cause voltage loss. In order to reduce the voltage loss at the interface and improve the efficiency of solar cells, it is an effective strategy to passivate the interface between the wide-band gap perovskite absorption layer and the C60 electron transport layer.
Passivation mechanism of perovskite surface
Li Yongfang/Meng Lei team conducted in-depth research on perovskite/organic laminated solar cells on the basis of previous research. They investigated the passivation mechanism of 1, 4-cyclohexanediamine molecules with cis-isomerism on wide-band gap perovskite surfaces (FIG. 1a), systematically revealing the difference in surface structure of perovskite caused by two cis-isomerized passivating agent molecules, and finally screened out the cis passivating molecule with the dominant configuration (CIS-CYDAI2).
The difference in the surface structure of perovskite caused by the molecular structure of the two passivating agents was studied in combination with theoretical calculation and X-ray. By studying the photoluminescence quantum yield of perovskite films treated with different passivating molecules, the corresponding quasi-Fermi level splitting was extracted. It is found that CIS-CYDAI2-treated perovskite films have higher theoretical open circuit voltage.
Further, by means of ultraviolet photoelectron spectroscopy and surface Kelvin force microscopy, they found that cis-CyDAI2 can cause the Fermi level on the surface of the wide-band gap perovskite to rise, weaken the surface pinning effect, and have better contact with the electron transport layer. Finally, the open circuit voltage of 1.36V and the photoelectric conversion efficiency of 18.4% were obtained in the wideband gap perovskite single junction cell with 1.88eV band gap. This strategy provides a new way to reduce voltage loss for wide-band gap perovskite solar cells.
Conclusion
The cooperation between Li Yongfang and Meng Lei's team and Professor Felix Lang of the University of Potsdam in Germany has achieved remarkable research results, which not only made a major breakthrough in the photoelectric conversion efficiency of perovskite-organic stacked solar cells, but also provided innovative solutions for improving the stability and practicality of the batteries. The research results not only show the advanced nature of the Chinese scientific research team in photovoltaic technology, but also provide valuable theoretical basis and technical support for the development of efficient and stable solar cells in the future.
Related articles: 12v 100ah lithium ion battery, blade battery, 18650 battery store, 21700 battery, commercial energy storage