Electronic structure, photoemission spectra, and vacuum-ultraviolet optical spectra of CsPbCl3and CsPbBr3

Optical spectra of CsPb${\mathrm{Cl}}_{3}$ and CsPb${\mathrm{Br}}_{3}$ have been measured in the range from 2 to 10 eV and have been combined with ultraviolet-photoemission-spectroscopy (UPS)---measurements at 21.1 and 40.8 eV. A quantitative band calculation is presented, which takes into account anion-anion interaction as well as electronic states of the ${\mathrm{Cs}}^{+}$ ion. The prominent features of earlier band models and measurements are reestablished through our measurements and calculations, namely that the valence band consists of anionic $p$ functions and Pb $6s$ functions, the lowest conduction band being Pb $6p$ type, and the lowest gap occuring at the $R$ point of the Brillouin zone. Inclusion of a further (Cs $6s$---type) conduction band, however, is necessary to bring the calculated joint density of states into agreement with vacuum-ultraviolet optical spectra. The calculated densities of states of the valence bands are in quantitative agreement with those deduced from our UPS measurements.