Atmospheric Pressure Chemical Vapor Deposition and Jet Vapor Deposition of CdTe for High Efficiency Thin Film PV Devices: Final Technical Report, 26 January 2000 - 15 August 2002

ITN’s three year project Atmospheric Pressure Chemical Vapor Deposition (APCVD) of CdTe for High Efficiency Thin Film PV Devices has the overall objectives of improving thin film CdTe PV manufacturing technology and increasing CdTe PV device power conversion efficiency. CdTe deposition by APCVD employs the same reaction chemistry as has been used to deposit 16% efficient CdTe PV films, i.e., close spaced sublimation, but employs forced convection rather than diffusion as a mechanism of mass transport. Tasks of the APCVD program center on demonstration of APCVD of CdTe films, discovery of fundamental mass transport parameters, application of established engineering principles to the deposition of CdTe films, and verification of reactor design principles which could be used to design high throughput, high yield manufacturing equipment. Additional tasks relate to improved device measurement and characterization procedures that can lead to a more fundamental understanding of CdTe PV device operation and ultimately to higher device conversion efficiency and greater stability. Under the APCVD program, device analysis goes beyond conventional one-dimensional device characterization and analysis toward two dimension measurements and modeling. Accomplishments of the concluding year and extension of the APCVD subcontract included: incorporation of HRT buffer layers and achievement of 12.3% efficient (NREL measured, but not certified) devices by APCVD; analysis of scale-up issues related to APCVD, analysis of dust formation dynamics; demonstration of the inherent deficiencies of APCVD for CdTe manufacturing; modeling effects of CdSTe and SnOx layers; and electrical modeling of grain boundaries. design and construction of a low-pressure jet vapor deposition (JVD) reactor; JVD CdTe film characterization as a function of substrate and source temperature; demonstration of high growth rates using JVD; and superstrate type and substrate type device fabrication using low substrate temperature JVD CdTe films.