LI Yongfang and MENG Lei’s research group at the Institute of Chemistry, Chinese Academy of Sciences (ICCAS), has made significant progress in wide bandgap perovskite solar cells (pero-SCs), by using 1,4-cyclohexanediamine iodide (CyDAI2) with cis-trans isomerism to passivate interface defects.

Pero-SCs have gained attention because of potential in photovoltaic field. By developing tandem solar cells (TSCs) that combine perovskites with other photovoltaic materials efficiency limit keep enhancing. Among these, perovskite-organic TSCs, which use wide bandgap pero-SC as front cell and narrow bandgap organic solar cell (OSC) as rear cell, stand out for their higher stability and solution-processable active layers.

Studies indicate that the front wide bandgap perovskites serve as UV filters, protecting the more delicate rear organic layers from damage caused by short-wavelength light. Additionally, the rear organic layers block moisture and oxygen, enhancing the stability of the front pero-SC. The interconnect layer (ICL) in TSCs also helps mitigate ion diffusion issues related to the electron-transporting layer in pero-SC, further improving stability.

Enhancing the voltage and efficiency of wide-bandgap pero-SCs is crucial for perovskite-organic TSCs. However, the interface between wide-bandgap perovskites and the C60 layer in the ICL often experiences electron recombination, leading to voltage losses. Addressing this issue requires effective methods to minimize these losses and boost overall TSC performance.

The researchers discovered that the cis configuration of CyDAI2 (cis-CyDAI2) outperforms the trans configuration, yielding a higher theoretical voltage and reduced energy loss. They achieved a high open circuit voltage of 1.36 V and a power conversion efficiency (PCE) of 18.4% for wide bandgap pero-SCs. By combining this with a ternary OSC as rear cell, the group set a record PCE of 26.4% for the perovskite-organic TSCs.

Figure. Chemical structure of CyDAI₂, analysis of voltage loss, structure of perovskite-organic tandem solar cells and the photovoltaic performance

Their paper, titled with "Isomeric diammonium passivation for perovskite-organic tandem solar cells" was published inNature(https://www.nature.com/articles/s41586-024-08160-y)(DOI:10.1038/s41586-024-08160-y)with JIANG Xin and Dr. QIN Shucheng at ICCAS as co-first authors, and Prof. MENG Lei, Prof. Felix Lang from the University of Potsdam, and Prof. LI Yongfang as corresponding authors. Supported by the National Natural Science Foundation of China and the Ministry of Science and Technology

Contact:

Prof. MENG Lei (menglei@iccas.ac.cn) or Prof. LI Yongfang (liyf@iccas.ac.cn)

Institute of Chemistry, Chinese Academy of Sciences