New results concerning the optical absorption, photoconductivity, photoluminescence and photoluminescence-excitation spectra of (CH3NH3)SnBr3 (3-D), (C6H5CH2CH2NH3)(2)SnI4 (2-D), Pt(en)(2) Pt(en)(2) Cl-2(ClO4)4 (1-D), CdxSy(SPh)(z) (0-D) and similar compounds (with:Pb, Ge instead of Sn; Pd, Ni instead of Pt; Se-y instead of S-y) are reported. The spectra exhibit strong excitonic bands and in some cases impurity-bands in the UV-visible-near infrared spectral region.