Research ArticleMATERIALS SCIENCE

Black phosphorus quantum dots in inorganic perovskite thin films for efficient photovoltaic application

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Science Advances  10 Apr 2020:
Vol. 6, no. 15, eaay5661
DOI: 10.1126/sciadv.aay5661
  • Fig. 1 Characterization of BPQDs.

    (A) TEM image. (B) Magnified TEM image (left) and HRTEM image (right) with a scale bar of 2 nm. (C) UV-visible absorption spectroscopy of BPQDs in a solvent mixture of DMF/DMSO (v:v = 9:1). Inset: Photograph of the solution of BPQD (15 mg ml−1). Photo credit Xiu Gong, Huazhong University of Science and Technology. (D) XPS spectroscopy for P 2p of BPQDs.

  • Fig. 2 BPQD-assisted deposition of perovskite films.

    SEM images of (A to D) CsPbI2Br films and (E to H) BPQDs@CsPbI2Br films consisting of 0.7 wt % of BPQDs annealed at a temperature range from 50° to 280°C for 2 min. The insets are the photographs of the corresponding samples. In situ variable-temperature XRD of (I) CsPbI2Br films and (J) BPQDs@CsPbI2Br films consisting of 0.7 wt % of BPQDs. a.u., arbitrary units. Photo credit Xiu Gong, Huazhong University of Science and Technology.

  • Fig. 3 CLSM characterizations.

    (A to C) Growth process of CsPbI2Br films as a function of increasing annealing temperatures [CsPbI2Br with perovskite phase, red fluorescence (59)] and (D to F) growth process of BPQDs@CsPbI2Br hybrid films consisting of 0.7 wt % BPQDs with augmentation of annealing temperatures [BPQDs, green fluorescence (60)] under excitation by 488- and 543-nm laser beams. Insets show the corresponding confocal microscopy images of the samples under bright field (scale bars, 5 μm).

  • Fig. 4 Adhesive energy calculation.

    Optimized geometrical structures and adhesive energies for PbI2/CsBr and CsBr/PbI2 adhesion on SnO2 substrates (A) and BPQD nucleation sites (B).

  • Fig. 5 CsPbI2Br solar cell devices with different addition amounts of BPQDs.

    (A) Schematic structure of the device and interaction between BPQDs and CsPbI2Br: The unbonded lone pairs of BPQDs offer excess electrons and facile interaction with cationic ions in CsPbI2Br, causing the CsPbI2Br nanocrystals formed to be attached onto BPQDs that supply effective heterogeneous nucleation sites. (B) Schematic diagram for CsPbI2Br growth onto the BPQDs surface. (C) Cross-sectional SEM image of the full device based on the BPQDs@CsPbI2Br hybrid film with 0.7 wt % of BPQDs. (D) Current density–voltage (J-V) curves and (E) EQE characteristics of the pristine devices and of the devices with various addition amounts (0.3 to 0.7 wt %) of BPQDs under different annealing temperatures.

  • Table 1 Device performance of perovskite solar cells.

    Pristine and differing weight volumes, x, of BPQDs.

    CsPbI2Br + xBPQDs*
    (black films)
    Jsc
    (mA/cm2)
    Jsc-AVE
    (mA/cm2)
    Voc
    (V)
    FF
    (%)
    PCE
    (%)
    PCEAVE
    (%)
    50°C/10 minx = 013.2311.52 ± 0.201.07649.268.97 ± 0.96
    x = 0.3 wt %13.9212.13 ± 0.111.096710.229.72 ± 0.74
    x = 0.5 wt %14.3813.47 ± 0.231.137211.7810.25 ± 0.94
    x = 0.7 wt %14.9513.61 ± 0.151.177513.2312.38 ± 0.84
    50–200°Cx = 0.7 wt %15.8614.85 ± 0.341.257815.4714.80 ± 0.76

    *All of the deposited perovskite films rested for 30 min before annealing in glove box.

    BPQDs@CsPbI2Br hybrid film with 0.7 wt % BPQDs was gradually annealed from 50° to 200°C at a ramp rate of 50°C (10 min)−1.

    Supplementary Materials

    • Supplementary Materials

      Black phosphorus quantum dots in inorganic perovskite thin films for efficient photovoltaic application

      Xiu Gong, Li Guan, Qingwei Li, Yan Li, Tao Zhang, Han Pan, Qiang Sun, Yan Shen, Carole Grätzel, Shaik M. Zakeeruddin, Michael Grätzel, Mingkui Wang

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      • Figs. S1 to S15
      • Tables S1 to S5

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