REACTION PATHWAYS TO CUINSE2 FORMATION FROM ELECTRODEPOSITED PRECURSORS

CuInSe2 thin films have been obtained from different precursors prepared by direct or sequential electrodeposition processes. The nature of the as-deposited layers and the evolution of the films during the heat-treatment in an inert (vacuum) or a reactive (elemental Se vapor) atmosphere have been studied by x-ray diffraction and x-ray photoelectron spectroscopy analysis. The chemistry of the different phase transformations occurring as a function of the annealing temperature has been examined, and possible reaction pathways for the formation of CuInSe2 are presented. The results show that high crystalline chalcopyrite CuInSe2 films with the desired composition can be obtained after annealing either direct or sequentially electrodeposited precursors at 400 degrees C. An improvement in film quality can be gained by using an electrodeposited Cu layer as growth surface for the CuInSe2 formation. If elemental Se is also added during the heat-treatment, then a higher recrystallization of the films is observed.