Validation of an in-line evaporation process for large-scale production of CuInSe2-based solar cells

The validation of an in-line manufacturing process for the fabrication of CuInSe₂-based solar cells (including the quaternary Cu[In,Ga]Se₂) has been demonstrated. The validation involves a fixed substrate (molybdenum-coated soda-lime glass) onto which the deposition of the compound is achieved via a method of variable metal fluxes. These variable metal fluxes emulate the fluxes as seen by a mobile substrate in an in-line two (or three)-source coevaporation system that evaporates the metals at a constant rate/flux. The importance of this in-line approach is based on its feasibility for large-area depositions and its efficient utilization of materials. These intrinsic advantages could have a great impact in the large-scale production of photovoltaic modules for terrestrial or space applications. The objectives of the present study are: (1) to determine which geometrical configuration of the in-line system yields the best device-quality materials; and (2) demonstrate that such a system can produce device-quality absorber materials that can be used for the fabrication of solar cells with efficiencies exceeding 10%. Polycrystalline thin films obtained by this approach have been characterized by electron probe for microanalysis (EPMA) and electron microscopy (SEM). Solar cells have been characterized by I-V and external quantum efficiency (QE) measurements