This paper presents the results of a study of the structural, optical, and photoelectric properties of single-crystal PbGa2S4 . The theory of direct optical transitions is used to determine the optical band gap of the indicated compound as Eg52.78 eV. The spectral dependences of the photocurrent at various temperatures and applied voltages show that local centers that arise during the production of the crystal are present inside the band gap. The position of the energy level of slow recombination centers (r centers) is found to be equal to 0.24 eV.
N. N. Musaeva, R. B. Dzhabbarov, U. F. Kasumov, and Kh. B. Ganbarova, "Optical and photoelectric properties of single-crystal PbGa2S4," J. Opt. Technol. 70, 676-679 (2003)