Chemical Bath Deposition of Cu-In-Se Based Thin Film Solar Cells on Flexible Substrates

Materials Research Group, Inc. proposes an innovative fabrication method for very low cost, high efficiency, multibandgap thin film photovoltaic converters on light weight plastic substrates. To date, CuInSe2 (CIS) based solar modules have the highest demonstrated efficiencies of any thin film photovoltaic material. All known deposition methods for CIS based materials use physical vapor deposition (PVD) at very high temperatures. MRG proposes a novel deposition method for CIS in which deposition temperatures are below 100 C. In this project, the chemical bath deposition (CBD) technique will be developed for the growth of CuInSe2 thin films on flexible substrates. CBD allows the growth of highly conformal, pinhole-free films, allowing the use of thinner (0.5 micron) CIS films than required when using PVD techniques (1-2 micron). Thinner films decrease indium usage, resulting in significant cost savings. This project will examine the growth of CIS films on molybdenum coated, flexible plastic substrates using CBD. A range of deposition conditions and various post-deposition heat treatments will be examined to determine the best method(s) for obtaining device quality film properties. Fabrication of complete solar cells will use CBD of CdS and sputtering of a conductive ZnO window layer on to the CIS film. The proposed research will result in a significant improvement in the power to weight ratio of solar modules. Combined with the ability to roll up the module for storage, this will provide a major advancement in non-nuclear space power generation.