Fig. 2: Characterizations of the dye-sensitized upconverting perovskite nanocrystal system.

a Representative TEM image of CsPbBr₃:Yb³⁺ nanocrystals. b Absorption spectra of CsPbBr₃:Yb³⁺ nanocrystals (in hexane), IR783-CsPbBr₃:Yb³⁺ nanocrystals (in hexane) and pure IR783 dye (in chloroform). c Upconversion luminescence spectra of IR783-CsPbBr₃:Yb³⁺ and IR780-CsPbBr₃:Yb³⁺ nanocrystals; the inset depicts a schematic of IR783 and IR780 molecules on the surface of CsPbBr₃:Yb³⁺ nanocrystals. d Upconversion luminescence spectra of CsPbBr₃:Yb³⁺ nanocrystals (red solid line), IR783-CsPbBr₃ nanocrystals (orange solid line), IR783-CsPbBr₃:Yb³⁺ nanocrystals (blue solid line), in contrast to the Stokes luminescence spectrum of IR783-CsPbBr₃:Yb³⁺ nanocrystals under 365 nm excitation (blue dashed line). Dye-sensitized upconversion spectra from IR783-CsPbBr₃:Yb³⁺ and IR780-CsPbBr₃:Yb³⁺ nanocrystals were acquired under 804 nm continuous-wave laser irradiance at 8.4 W/cm², while upconversion spectra from CsPbBr₃:Yb³⁺ nanocrystals were acquired under 980 nm continuous-wave laser irradiance at 8.4 Wcm⁻².