Fig. 5: Optoelectronic properties of lead sulfohalide NCs and Pb4S3Cl2/CsPbCl3 heterostructures.
a Absorption (ABS, solid lines) and photoluminescence (PL, dashed lines) spectra of free-standing Pb3S2Cl2, Pb4S3Cl2, CsPbCl3 NCs and of Pb4S3Cl2/CsPbCl3 heterostructures. The CsPbCl3 NCs were prepared for comparison purposes by heating the CsPbCl3 precursor nanoclusters (see Supplementary Discussion, section 6). b Decay curves of the ∼410 nm PL from CsPbCl3 as free-standing NCs and in the Pb4S3Cl2/CsPbCl3 heterostructures. The dashed gray line is the time response of the experimental setup. Inset: PL spectra of CsPbCl3 as free-standing NCs and in the heterostructures, showing a drastic quenching in the latter case. The PL intensity of the heterostructures is multiplied ×10 to make it more visible. The slight redshift of the heterostructure PL maximum is likely due to the relaxation of quantum confinement of the perovskite domain caused by the partial delocalization of the exciton in the chalcohalide domain. c Decay curves of the ∼1.8 eV (∼690 nm) emission of the three samples at room temperature and at 77 K (inset). Color code for a–c: cyan = CsPbCl3, blue = Pb4S3Cl2, orange = Pb3S2Cl2, black = Pb4S3Cl2/CsPbCl3 heterostructures. d Electronic structure of free-standing Pb3S2Cl2 (left) and Pb4S3Cl2 (right) NC models computed at the DFT/PBE level of theory. The color code indicates the elemental contribution to each molecular orbital (Pb = gray; S = yellow; Cl = green). e Electronic structure of the Pb4S3Cl2/CsPbCl3 heterostructure model computed at the DFT/PBE level of theory, color coded by domain (Pb4S3Cl2 = orange; CsPbCl3 = cyan). The Inverse Participation Ratio (IPR, left panel) quantifies the degree of localization of a state (1/Natoms = completely delocalized; 1 = localized on one single atom), and indicates that most of the states surrounding the band gap are localized trap states. f Representation of molecular orbitals corresponding to band edge delocalized states (1,4) and to band edge trap states (2,3). In both cases, the band edge states are localized on the Pb4S3Cl2 domain. Source data for a–e are provided as a Source Data file.
