Large-area flexible, transparent, and highly luminescent films containing lanthanide (III) complex-doped ionic liquids for efficiency enhancement of silicon-based heterojunction solar cell.

ABSTRACT Ionic liquid (IL)-based lanthanide luminescent materials with luminescent downshifting properties are beneficial for enhancing the photovoltaic energy conversion efficiency ( η_pv) of silicon-based solar cells. Herein, novel lanthanide (III) complex-doped ILs have been successfully prepared by simply dissolving the complex Ln(pybox)₃ (Ln = Eu or Tb, pybox = 2,6-bis[(4 R)-4-phenyl-2-oxazolinyl]pyridine) into a bidentate organophosphine functionalized IL (1,3-bis-[3-(diphenylphosphinyl)propyl]imidazolebis (trifluoromethylsulfonyl)imide), showing improved luminescence efficiency attributed to the coordination of ILs with Ln³⁺ ions and thus occurrence of the energy transfer from ILs to Ln³⁺ ions and very high absolute quantum efficiency (up to 97.22%). Large area (17 × 17 cm²) flexible, transparent, and luminescent poly(methyl methacrylate) thin films were prepared through a simple drop-casting method and were applied as luminescent downshifting coatings to the silicon-based heterojunction solar cells (active area: 235 cm²). In the best case using the Tb³⁺-containing film, the η_pv of the solar cell increases from 16.676 to 16.774%. [ABSTRACT FROM AUTHOR]