Extended Data Fig. 2: DFT simulation on the coordination.

The binding energies (BE) between DMSO or PTSH molecules and PbI2 or SnI2, respectively. Where white, brown, light blue, red, yellow, ice blue, and black balls are H, C, N, O, S, Sn, and Pb atoms. The BE of PTSH molecules with Sn2+ for SnI2 and Pb2+ for PbI2 are −2.112 eV and −1.817 eV, respectively, which are higher than the binding energies of DMSO molecules with Sn2+ for SnI2 (−1.613 eV) and Pb2+ for PbI2 (−1.434 eV).