Design Strategy for Scale-Up of Physical Vapor Deposition of Cu(InGa) Se2 on Flexible Substrates

Abstract

It has been observed that scale-up of the Cu(InGa)Se2 Physical Vapor Deposition (PVD) onto flexible substrates to wide webs and long runtimes will lead to unacceptable film qualities due to issues associated with the thermal characteristics of the source-boats and the effect of melt level reduction with time. These issues are the subject of the present paper. The difficulties encountered with the design of the sources presently in operation are addressed, and new designs are proposed that resolve the problem of thickness and composition uniformity over wider substrates (~12 inches). Simulation results are presented comparing the old source design with the proposed new one for a 12-inch wide substrate. It is shown that improved film thickness uniformity and hence composition uniformity is achieved with the proposed designs, and material utilization can be improved by an appropriate choice of system design parameters such as nozzle-to-substrate distance.