Table 2. Experimental Details and Parameters of Synthesis with Different Precursor Concentrationsa.
| molar ratio | Pb:Sn = 1:0 | Pb:Sn = 1:1 | Pb:Sn = 1:2.5 | Pb:Sn = 3.5:0 | Pb:Sn = 1:5 |
|---|---|---|---|---|---|
| [Pb] (mmol) | 0.166 | 0.166 | 0.166 | 0.581 | 0.166 |
| [Sn] (mmol) | 0 | 0.166 | 0.415 | 0 | 0.830 |
| [Br] (mmol) | 0.332 | 0.664 | 1.162 | 1.162 | 1.992 |
| PL (nm) | 513 | 509 | 503 | 507 | 488 |
| FWHM | 22.0 | 21.4 | 21.2 | 23.0 | 30.1 |
| PLQY (%) | 7.3 ± 1.2 | 62.8 ± 1.0 | 73.4 ± 0.9 | 45.7 ± 1.7 | 26.4 ± 3.3 |
| Bandgap (eV) | ∧ | 2.39 | 2.43 | 2.38 | 2.43 |
| Stokes shift | ∧ | 10 nm | 10 nm | 16 nm | 14 nm |
| 50.0 meV | 50.0 meV | 79.7 meV | 75.0 meV | ||
| XRD | * | #/* | #/* | */# | * |
| Average Sn % | 0 | 4.0 ± 1.0 | 7.0 ± 2.0 | 0 | 12.0 ± 3.0 |
| Average size (nm) | 17.89 ± 2.73 | 10.81 ± 1.27 | 6.18 ± 0.48 | 9.18 ± 1.14 | 84.97 ± 6.58 |
Reaction temperature and reaction time were fixed to 150 °C and 5 s, respectively. The amount of Pb, Sn, and Br, introduced by PbBr2 and SnBr2 precursors, is indicated, while the amount of Cs-oleate precursor is fixed to 0.045 mmol. Two conditions for pure-Pb NP have been investigated, one with 0.166 mmol of PbBr2 (ratio 1:0) and the other with a 3.5 times higher amount (ratio 3.5:0). Optical properties of the synthesized NPs have been measured on solution after synthesis and after washing allowing the following to be determined: the PL peak position, the full width at half-maximum (FWHM) of the PL peak, the PLQY, the bandgap extracted from the analysis of the Tauc plots of the absorption measurements, and finally the Stokes shift between light absorption and emission. The bandgap and Stokes shift are not indicated for samples with ratio 1:0, as no clear band edge was observed. XRD indicates the crystalline compounds detected by XRD, see Figure 1a, # = CsPbBr3 cubic phase (ICDS 109295) and * = Cs4PbBr6 tetragonal phase (ICDS 162158), where X is Pb and Sn, the % of Sn measured by EDX during the TEM characterization is also indicated. The average size of the nanoparticles obtained by the statistical analysis of TEM images is also indicated; more detailed histograms with NP size can be found in Figure S9. ∧ = For the Pb:Sn 1:0 sample, the absorption band edge was not easy to determine from the experimental results and consequently the bandgap and the Stokes shift cannot be calculated without a big error.