Quaternary alkylammonium salt dopants for Spiro-OMeTAD

• Ionic salt dopants designed to replace lithium bis(trifluoromethane )sulfonyl imide (Li-TFSI) for doping the widely used spiro-OMeTAD hole transport material in perovskite solar cells (PSCs) have been reported to effectively suppress the undesirable side effects caused by TFSI . However, the role of cationic molecules and their potential interactions with the underlying perovskite film surface have remained largely unexplored.

  
  

  Here, Il Jeon and Jin-Wook Lee et al. from Sungkyunkwan University found that ionic salts introduced into the spiro-OMeTAD layer can chemically interact with the underlying perovskite to induce interfacial reactions. Inspired by this interaction, a strategy is proposed that benefits from the interfacial reaction between the cations used for dopants and the underlying perovskite film surface to passivate surface defects. A simple alkyl quaternary ammonium salt, tetramethylammonium bis(trifluoromethanesulfonyl )imide (TMA-TFSI), is strategically employed to demonstrate a proof-of-concept device. TMA-TFSI not only acts as an efficient dopant for oxidized spiro-OMeTAD with enhanced environmental stability, but also forms a one-dimensional passivation layer via interfacial reactions with the underlying perovskite film surface.

  
  

  As a result, the operation and environmental stability of PSCs are significantly enhanced along with the increase in power output. This work should provide important insights into the design of effective ionic salt dopants for PSCs to simultaneously improve both performance and operation stability.

  
  

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• S.-K. Jung, K. Park, J.-H. Lee, S.-G. Choi, JS Choi, SM Kang, I. Jeon, J.-W. Lee, Exploiting an Interfacial Reaction in Perovskite Solar Cells: Quaternary Alkylammonium Ionic Salt Dopants for Spiro-OMeTAD. Adv. Energy Mater. 2024, 2402144.

  
  

  https://doi.org/10.1002/aenm.202402144