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Color-pure red light-emitting diodes based on two-dimensional lead-free perovskites

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Science Advances  14 Oct 2020:
Vol. 6, no. 42, eabb0253
DOI: 10.1126/sciadv.abb0253
  • Fig. 1 Interactions between VA and perovskite precursors and perovskite films.

    1H NMR (A) and 13C NMR (B) spectra of VA, VA + PEAI, and VA + SnI2 in DMSO-d6 solution. a.u., arbitrary unit. (C) FTIR spectra of PEA2SnI4 film prepared with and without VA. (D) Representation of hydrogen bonding (O─HI) and coordination bonding (C═OSn) interactions between VA and PEA2SnI4 crystals. High-resolution Sn3d XPS spectra of PEA2SnI4 films prepared with (F) and without (E) VA. Pristine films were prepared with the precursors containing metallic Sn powder.

  • Fig. 2 Crystallization kinetics and structural characterization of PEA2SnI4 films.

    SEM image of PEA2SnI4 films prepared without (A) and with (B) VA. (C) High-resolution XRD spectra (in the range from 5° to 6°) of PEA2SnI4 films prepared with and without VA. In situ GIWAXS measurements of spin-coated PEA2SnI4 without (D) and with (E) VA at different times.

  • Fig. 3 Optical properties and carrier dynamics in PEA2SnI4.

    (A) Absorption and PL spectra of PEA2SnI4 films (inset shows the light emission image under UV light excitation). (B) Time-resolved PL and corresponding fits of PEA2SnI4 films prepared with and without VA. Two-dimensional pseudocolor map of fs-TA spectra of PEA2SnI4 films prepared without (C) and with (D) VA expressed as ΔOD (the change of the absorption intensity of the sample after excitation at 650 nm) as a function of both delay time and probe wavelength. (E) TA signal of PEA2SnI4 films at 612 nm with an excitation wavelength of 650 nm at a corresponding delay time of 0.4 ps. Here, the ΔOD is normalized to the linear OD at each wavelength to allow for quantitative comparison. (F) The normalized emission intensity of PEA2SnI4 films prepared with and without VA after storing for 3 months.

  • Fig. 4 LED structure, energy diagram, and performance.

    (A) Device structure, (B) energy level diagram, (C) EL spectra, and (D) normalized EL spectra of PEA2SnI4 LEDs at different operation voltage. (Inset is the operation photograph of the red LEDs operated at 7 V.) (E) Color coordinate in the CIE 1931 chromaticity diagram of the EL spectra. (F) Luminance–voltage–current density and (G) EQE–current density characteristics, and (H) operational lifetimes and (I) emission spectra as functions of device operation time.

  • Table 1 Key optical parameters of red emitters for LED applications.

    Materials category and exampleEmission peak
    (nm)
    FWHM (nm)CIEDistance to Rec.
    2100
    Reference
    Cd-based QDsCdSe@CdS64030(0.71, 0.29)0.003(12)
    Pb-based QDsCsPb(Br/I)364933(0.72, 0.28)0.017(13)
    CsPbl367540NANA(14)
    In-based QDsInP/ZnSe/ZnS63050–60(0.69, 0.31)0.026(15)
    Organic moleculeDBP610>60(0.61, 0.39)0.14(16)
    Inorganic semiconductorsGaAlAs>640>25(0.72, 0.28)0.017(17)
    Sn-basedPEA2Snl463221(0.708, 0.292)0This work

Supplementary Materials

  • Supplementary Materials

    Color-pure red light-emitting diodes based on two-dimensional lead-free perovskites

    Fanglong Yuan, Xiaopeng Zheng, Andrew Johnston, Ya-Kun Wang, Chun Zhou, Yitong Dong, Bin Chen, Haijie Chen, James Z. Fan, Geetu Sharma, Peicheng Li, Yuan Gao, Oleksandr Voznyy, Hao-Ting Kung, Zheng-Hong Lu, Osman M. Bakr, Edward H. Sargent

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