Peculiarities of manifestation of different forms of structure disorderingin the exciton spectra of the PbI2

For an express reveal of defects of different nature in single crystals of PbI2 a method highly sensitive to structure changes, based on the measure o f low-temperature (T = 4.5 K) exciton spectra of light reflection (RS) and photoluminescence (PL), has been used. The doping of PbI2 with impurities ( In, Ga, Ag, Cu, Cd, Fe, Mn, Ni) promotes preferably the creation of the 4H- polytype in the process of growth and one-dimensional structure disordering . The high coefficient values of the concentration shift and broadening of substitutional solid solution (SSS) of Pb1-xMnxI2 and Pb1-xCdxI2 exciton ba nd are explained by the realization of conditions for the creation of the 4 H-PbI2-cluster phase. In the PL spectra of some samples representing joints of 2H+4H-polytypes, an additional D band (lambda = 499.2 nm, T = 5 K) has been revealed. The D band is characterized by the coefficient of temperatur e shift dE/dT = -0.25 x 10(-3) eV/K which is not proper to bands connected with defects.