GRAIN-BOUNDARY CONDUCTIVITY IN DIFFERENT POLYCRYSTALLINE MOSE2 THIN-FILMS

It has been shown early that curved plots for the conductivity of poly crystalline diselenide molybdenum were systematically obtained whateve r the technique used for the obtention of the layers. In the general c ase of polycrystalline semiconductors these deviations from the simple thermoionic emission across the grain boundaries have been recently a ttributed to potential fluctuations at the grain boundaries. Here a go od agreement between the experimental results and this new theory is o btained. The result deduced from theoretical propositions is conforted by the scanning electron micrographs of the layers and other preceedi ng experimental studies. In the light of the discussion of the MoSe2 l ayers, a quality factor Q is proposed for photovoltaic thin films. Thi s estimation shows that the films obtained by solid state reaction and substitution are the best. Mo and Te thin films are sequentially depo sited. Then an annealing under Se and Te pressure at 770 K for 24 h gi ves crystallized and stoichiometric MoSe2 thin films. These films have the higher quality factor among the films studied here (Q = 0.75). Th is is in close agreement with the good electrical and optical properti es of these layers.