Critical issues in vapor deposition of Cu(InGa)Se2 on polymer web: source spitting and back contact cracking

This paper presents solutions to two critical problems encountered during the physical vapor deposition of Cu(InGa)Se₂ films on Mo coated polymer web in a roll-to-roll reactor. Spitting out of the Cu source, resulting in Cu-rich particles imbedded in the growing films and causing shorts in the devices, has been eliminated by changing the shape of the effusion nozzles. Sources having conical nozzles eliminated the spitting by reducing the temperature gradient along the nozzle. Heavy cracking of the Mo back contact film during the deposition of the Cu(InGa)Se₂ films has been found to be related to the reaction of Mo with Se in the reactor. Introducing an appropriate amount of oxygen into the Mo film eliminated the cracking by reducing the reactivity of the film to Se.