Electronic properties of three- and low-dimensional semiconducting materials with Pb halide and Sn halide units

Band-structure calculations, semiempirical as well as ab initio, have been applied to study the electronic band gap of the new exotic natural low-dimensional MX systems (where M = Pb or Sn and X = I, Br or Cl). Moreover, variational calculations are employed to calculate the excitonic binding energies, whose amplification is due not only to the quantum confinement of the excitons but also to a dielectric enhancement effect. A single set of semiempirical parameters is sought to describe the materials; comparison of the calculations with experimental data shows this to be successful in the case of the PbI- and PbBr-containing compounds.