China: Record-breaking PV-organic solar cells hit 26.4% efficiency

According to the researchers, the novel cell employs wide-bandgap perovskite materials to capture short-wavelength sunlight and a narrow-bandgap organic active layer to absorb long-wavelength sun rays.

Bojan Stojkovski

Representational image of a perovskite high performance solar cell module

iStock/audioundwerbung

A team of international scientists associated with the Institute of Chemistry, Chinese Academy of Sciences, has developed the next generation high-efficiency solar cell, termed the perovskite-organic tandem solar cell.

Li Yongfang, a researcher who was part of the team, noted that the perovskite-organic tandem solar cell can reach a record photoelectric conversion efficiency of 26.4%, showcasing the potential of perovskite materials in enhancing solar energy efficiency. The conversion efficiency beats other such solar cells produced so far.

Li added that the novel cell employs wide-bandgap perovskite materials to capture short-wavelength sunlight and a narrow-bandgap organic active layer to absorb near-infrared long-wavelength sun rays. He noted that this combination greatly broadens the usable solar spectrum and significantly improves the device’s energy conversion efficiency.

Dubbed as the next generation of solar technology, perovskite solar cells and organic solar cells provide numerous benefits such as easier preparation, lightweight construction, as well as the potential for flexible device fabrication.

These features offer significant potential for applications in portable energy, building-integrated photovoltaics, and indoor photovoltaics. Perovskite has been commonly used in series-connected monolithic tandem solar cells (TSCs) to surpass the Shockley-Queisser limit of single-junction solar cells. Perovskite/organic TSCs, which feature a wide-bandgap perovskite solar cell at the front and a narrow-bandgap organic solar cell at the back, have gained popularity for their stability and potential for high power conversion efficiency.

The new breakthrough adds to a recent achievement by a team of researchers from Huazhong University of Science and Technology in China, who reached a record power conversion efficiency of 28.49% for an all-perovskite tandem solar cell.

Previous research has shown that bulky cations, such as cyclic or aromatic diammonium cations, are often used to passivate the surfaces of 3D perovskite films or in Dion-Jacobson (DJ) 2D perovskites. Authors of the study note that isomeric structures may exist in some diammonium cations, and their effects on passivation require further investigation.

They explain that the position of functional groups, like ammonium and fluorine, significantly influences electron cloud distribution and intramolecular dipoles, leading to different interactions with the 3D perovskite film surface. Importantly, cis-trans isomerism provides molecular rigidity, helping to maintain a strong dipole moment.

To address voltage loss from interfacial recombination at the wide-bandgap perovskite/C60 interface, the researchers propose using isomeric diammonium salts for surface passivation. They selected cyclohexane-1,4-diammonium diiodide (CyDAI2), which has two isomeric forms: cis-CyDAI2 and trans-CyDAI2, with ammonium groups on the same side or opposite sides of the cyclohexane ring.

Thus, using the isomeric diammonium passivation strategy, particularly with cis-CyDAI2, can greatly improve the performance of wide-bandgap perovskite solar cells, leading to more efficient and stable perovskite/organic tandem solar cells.

By comparing the effects of these two isomers on wide-bandgap perovskite films, the authors aim to find the best method for reducing interfacial recombination, increasing open-circuit voltage, and improving device stability.

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Bojan Stojkovski Bojan Stojkovski is a freelance journalist based in Skopje, North Macedonia, covering foreign policy and technology for more than a decade. His work has appeared in Foreign Policy, ZDNet, and Nature.

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