Research ArticleSURFACE CHEMISTRY

Enhanced mobility CsPbI3 quantum dot arrays for record-efficiency, high-voltage photovoltaic cells

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Science Advances  27 Oct 2017:
Vol. 3, no. 10, eaao4204
DOI: 10.1126/sciadv.aao4204
  • Fig. 1 High-efficiency FAI-coated CsPbI3 QDSCs.

    (A) Schematic cross section of a solar cell. FTO, fluorine-doped tin oxide. (B) SEM image of a device cross section. (C to E) NREL-certified (C) J-V characteristics from forward bias to reverse bias, (D) stabilized current at a constant voltage of 0.95 V, and (E) EQE.

  • Fig. 2 Effect of AX salts on CsPbI3 QD films and PV performance.

    (A) Schematic of the film deposition process and AX salt posttreatment. (B) J-V characteristics of CsPbI3 QD devices treated with FAI (pink), methylammonium iodide (MAI) (green), formamidinium bromide (FABr) (yellow), methylammonium bromide (MABr) (gray), cesium iodide (CsI) (dark blue), and neat EtOAc control (blue). (C and D) ToF-SIMS depth profile of CsPbI3 QD films (C) without and (D) with an FAI posttreatment. Intensity is normalized to total counts at each data point. (E) Ratios of Cs/Pb, I/Pb, and FA/Pb calculated from the integrated ToF-SIMS signal intensities throughout the film. int., integrated; arb., arbitrary.

  • Fig. 3 Confinement in FAI-coated films.

    (A) Normalized (norm.) PL of CsPbI3 QD films fabricated with three different sizes (as indicated by the injection temperature during synthesis) of QDs with (pink) and without (blue) FAI treatment. (B and C) AFM images of CsPbI3 QD films (B) without and (C) with an FAI posttreatment.

  • Fig. 4 Improved mobility with FAI coating.

    (A) Time-domain terahertz pulses through each of the films described in the text recorded at a pump delay time of ~1ps. (B) Time-resolved terahertz photoconductivity measurements of the films of CsPbI3 control sample (blue) compared to the FAI-coated CsPbI3 QD films (pink) along with a traditional MAPbI3 (black) thin film and films of 6-nm PbSe QDs (orange) and 3-nm PbS QDs (green). (C and D) Comparison of the extracted (C) mobility and (D) terahertz lifetimes for each of the films.

  • Table 1 Effect of AX salts on PV parameters extracted from J-V scans.
    AX salt posttreatmentVOC (V)JSC (mA cm−2)FFPCE (%)
    FAI (EtOAc)1.2014.370.7813.4
    FABr (EtOAc)1.2212.700.8112.6
    MAI (EtOAc)1.2013.390.7912.6
    MABr (EtOAc)1.2111.270.8211.2
    CsI (EtOAc)1.2010.640.8110.3
    Neat EtOAc1.179.220.788.5

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/3/10/eaao4204/DC1

    Supplementary Materials and Methods

    fig. S1. Performance of FAI-coated and control devices.

    fig. S2. Light absorption following FAI posttreatment.

    fig. S3. Comparison of EQE with AX posttreatment.

    fig. S4. Reproducibility of FAI-coated CsPbI3 QD device performance.

    fig. S5. XPS spectroscopy.

    fig. S6. FTIR spectra of CsPbI3 QDs.

    fig. S7. Crystal structure of CsPbI3 QDs.

    fig. S8. CsPbI3 QD film morphology.

    fig. S9. Comparison of terahertz μs × τ product.

    fig. S10. PL lifetime of CsPbI3.

    Reference (34)

  • Supplementary Materials

    This PDF file includes:

    • Supplementary Materials and Methods
    • fig. S1. Performance of FAI-coated and control devices.
    • fig. S2. Light absorption following FAI posttreatment.
    • fig. S3. Comparison of EQE with AX posttreatment.
    • fig. S4. Reproducibility of FAI-coated CsPbI3 QD device performance.
    • fig. S5. XPS spectroscopy.
    • fig. S6. FTIR spectra of CsPbI3 QDs.
    • fig. S7. Crystal structure of CsPbI3 QDs.
    • fig. S8. CsPbI3 QD film morphology.
    • fig. S9. Comparison of terahertz μs × τ product.
    • fig. S10. PL lifetime of CsPbI3.
    • Reference (34)

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