CIS Photovoltaic Technology: Thin-Film Partnership Program, Annual Technical Report, 12 January 1996 - 11 January 1997

This report describes work performed during the second year of a three-phase, 3-year, cost-shared subcontract . The subcontract is one component of the NREL Thin Film PV Partnership Program. Energy Photovoltaics, Inc. (EPV) explored novel CIGS formation recipes that can be implemented on a unique pilot line constructed to coat substrates 4300 cm2 in area. One particular feature of this line isthe use of linear sources capable of downwards evaporation. EPV experimented with several types of recipe, and a 'hybrid' process was found to simultaneously yield the desired combination of properties--good adhesion, device efficiency, uniformity, and reproducibilty. At the device level, significant results were obtained using alternative buffer layers, direct ZnO devices, and chemicaltreatment of the CIGS, and a new method was developed and transferred to NREL to enable measurement of device-specific internal resistance. Also, considerable effort was put into complete module fabrication, testing, and analysis. A reliable procedure for laser scribing the molybdenum was developed, the chemical-bath deposition of the thin CdS layer was made more efficient in terms of materialuse, the bipolar sputtering process for large-area ZnO was further optimized to yield films with 80% transmission and less than 30 ohms/square sheet resistance, and a new, non-destructive technique was developed to obtain local I-V curves at selected locations on a patterned plate. A fully encapsulated 3156-cm2 CIGS module sent to NREL for testing produced 19.7 W in sunlight at 997 W/m2irradiance, corresponding to an aperture-area efficiency of 6.25%.