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Title: Advanced CIGS Photovoltaic Technology: Annual Technical Report, 15 November 2001-14 November 2002

Abstract

Energy Photovoltaics, Inc. (EPV) has consistently pursued a vacuum-based approach to CIGS production, using novel linear-source technology and standard soda-lime glass substrates. It has also chosen to develop processing methods with worker safety in mind. These choices result in layers having controllable purity and low physical defects, and production without significant hazards. Considerations such as these are important in helping to minimize the processing costs of CIGS. Technically, thin-film PV technologies have advanced considerably in the last few years. EPV successfully produced high-quality 0.43m2 Mo-coated glass substrates that, when cut, enabled NREL to produce 17.1% CIGS cells on such substrates. EPV successfully used novel linear evaporative sources for supply of Cu, In, Ga, and Se to form CIGS on 0.43m2 substrates, producing modules with Voc's of up to 37 V. A new approach to buffer-layer deposition was pioneered through synthesis of the compound ZnIn2Se4 and its use as a source material. In addition, the current generated in exploratory a-Si/a-Si/CIGS stacked devices was increased from 6 to 13 mA/cm2. Supporting these programs, EPV's upgraded analytical laboratories provided rapid in-house feedback concerning material and device properties. The objective of this subcontract is to develop and assemble the various pieces of new technologymore » that EPV considers essential for cost-effective production of CIGS modules. The long-term objective of the Thin Film PV Partnership Program is to demonstrate low-cost, reproducible modules of 15% aperture-area efficiency.« less

Authors:
;
Publication Date:
Research Org.:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
15003960
Report Number(s):
NREL/SR-520-33836
ZDJ-2-30630-21; TRN: US201015%%247
DOE Contract Number:
AC36-99-GO10337
Resource Type:
Technical Report
Resource Relation:
Related Information: Work performed by Energy Photovoltaics, Inc., Princeton, New Jersey
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; 36 MATERIALS SCIENCE; AVAILABILITY; DEFECTS; DEPOSITION; EFFICIENCY; FEEDBACK; GLASS; PROCESSING; PRODUCTION; SAFETY; SUBSTRATES; SYNTHESIS; THIN FILMS; PV; CIGS CELLS; I-V CURVE; QUANTUM EFFICIENCY; MANUFACTURING; JUNCTION FORMATION; POST-DEPOSITION TREATMENT; Solar Energy - Photovoltaics

Citation Formats

Delahoy, A. E., and Chen, L. Advanced CIGS Photovoltaic Technology: Annual Technical Report, 15 November 2001-14 November 2002. United States: N. p., 2003. Web. doi:10.2172/15003960.
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Delahoy, A. E., & Chen, L. Advanced CIGS Photovoltaic Technology: Annual Technical Report, 15 November 2001-14 November 2002. United States. doi:10.2172/15003960.
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Delahoy, A. E., and Chen, L. Thu . "Advanced CIGS Photovoltaic Technology: Annual Technical Report, 15 November 2001-14 November 2002". United States. doi:10.2172/15003960. https://www.osti.gov/servlets/purl/15003960.
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@article{osti_15003960,
title = {Advanced CIGS Photovoltaic Technology: Annual Technical Report, 15 November 2001-14 November 2002},
author = {Delahoy, A. E. and Chen, L.},
abstractNote = {Energy Photovoltaics, Inc. (EPV) has consistently pursued a vacuum-based approach to CIGS production, using novel linear-source technology and standard soda-lime glass substrates. It has also chosen to develop processing methods with worker safety in mind. These choices result in layers having controllable purity and low physical defects, and production without significant hazards. Considerations such as these are important in helping to minimize the processing costs of CIGS. Technically, thin-film PV technologies have advanced considerably in the last few years. EPV successfully produced high-quality 0.43m2 Mo-coated glass substrates that, when cut, enabled NREL to produce 17.1% CIGS cells on such substrates. EPV successfully used novel linear evaporative sources for supply of Cu, In, Ga, and Se to form CIGS on 0.43m2 substrates, producing modules with Voc's of up to 37 V. A new approach to buffer-layer deposition was pioneered through synthesis of the compound ZnIn2Se4 and its use as a source material. In addition, the current generated in exploratory a-Si/a-Si/CIGS stacked devices was increased from 6 to 13 mA/cm2. Supporting these programs, EPV's upgraded analytical laboratories provided rapid in-house feedback concerning material and device properties. The objective of this subcontract is to develop and assemble the various pieces of new technology that EPV considers essential for cost-effective production of CIGS modules. The long-term objective of the Thin Film PV Partnership Program is to demonstrate low-cost, reproducible modules of 15% aperture-area efficiency.},
doi = {10.2172/15003960},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Thu May 01 00:00:00 EDT 2003},
month = {Thu May 01 00:00:00 EDT 2003}
}
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Technical Report:
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DOI:  10.2172/15003960
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  • ;
    The objective of this subcontract is to develop and integrate the various pieces of new technology that EPV considers enabling for cost-effective production of CIGS modules. EPV has conducted research to help generate a technology base for production of CIGS PV modules using vacuum deposition of CIGS onto glass. This strategy is consistent with the observation that, despite there being several approaches to forming device-quality CIGS, vacuum deposition has maintained the world record for the highest-efficiency CIGS device. A record thin-film solar cell efficiency of 19.2% (with Ni-Al grid and MgF2 ARC) for a 0.41-cm2 device was achieved by NRELmore » in 2003 using vacuum-deposited CIGS. The deposition employed four point sources and detection of the Cu-poor to Cu-rich transition for process control. To extend this type of processing to the realm of large-area substrates, EPV developed vacuum equipment designed for heating and coating 0.43-m2 moving substrates, with a projected further scale up to 0.79 m2. The substrates are typically low-cost, soda-lime glass, and the materials are supplied to the moving substrates using novel linear-source technology developed by EPV. The use of elemental selenium rather than toxic H2Se gas helps make for a safe manufacturing environment. These choices concerning film deposition, substrates, and source materials help to minimize the processing costs of CIGS.« less

  • ;
    The principal objective of Energy Photovoltaics, Inc., is to develop the best CIGS large-area module process based on capability of implementation on EPV's large-scale processing equipment. The first requirement was to develop recipes for CIGS, junction formation, and a high-quality ZnO window that together are capable of producing small-area devices with efficiencies in excess of 13%. The second requirement was to significantly improve the uniformity of all layers (Mo, CIGS, CdS, and ZnO) on large-area substrates. Thirdly, patterning procedures needed to be improved to generate an interconnection with the lowest possible contact resistance, to eliminate possible shunting paths, and tomore » reduce the dead area. The processes should have good reproducibility and therefore be easily controllable. Finally, having assembled all of these aspects mentioned above, the goal was to fabricate large-area, monolithic CIGS modules with efficiencies in the range 7%-10%. A study of module reliability and long-term stability would be conducted to establish the foundation and confidence for embarking on future manufacturing.« less

  • ; ; ; ...
    This report describes the state-of-the-art capabilities that were demonstrated for Mo, CIGS, and ZnO depositions at coating widths of 45 cm. The CIGS is formed by linear-source evaporation onto moving substrates using multiple line sources. The linear sources were characterized according to deposition uniformity and angular dependence of emitted flux. Uniformity maps were generated for CIGS composition and device performance over large areas. Large-area CIGS modules were produced with Voc's up to 36.9 V. High-Ga-content CIGS devices were produced in the pilot-line system with an efficiency of 11.2% (Voc 596 mV, Jsc 27.4 mA/cm2, FF 67.7%). The minimum bandgap inmore » R&D CIGS was successfully controlled through Ga content and Ga profile. A reliable recipe was developed that yielded a best efficiency of 12.4% (Voc 532 mV, Jsc 34.3 mA/cm2, FF 67.9%). A promising source material (ZnIn2Se4) was synthesized and used for buffer layer deposition, resulting in an 11.6% cell on NREL CIGS (Voc 562 mV, Jsc 30.8 mA/cm2, FF 67.2%). Deposition rate from a charge of ZIS was recorded as a function of evaporation time and source temperature. Current generated in the CIGS component of an a-Si/a-Si/CIGS stacked device was increased from 5.6 to 12.9 mA/cm2. Useful gains in conductivity and transmission of large-area sputtered ZnO:Al were obtained through use of substrate heating. EPV is constructing an entirely new CIGS pilot line for scale up and limited manufacturing purposes. The coating width is 65 cm. The company's analytical capabilities have been upgraded with the installation of ICP, SEM/EDS, computerized QE, and stylus profilometer facilities.« less

  • ; ; ; ...
    This report describes work performed by Energy Photovoltaics, Inc. (EPV) under Phase I of this subcontract. EPV's new FORNAX process for CIGS formation is capable of producing devices with high V{sub oc} (>600 mV) and no dark aging effects. Parameters of the best device so far are V{sub oc} = 611 mV, J{sub sc} = 27.5 mA/cm{sup 2}, FF = 74.5%, and efficiency = 12.5%. A 34-cm{sup 2} 16-cell minimodule was produced using FORNAX CIGS with V{sub oc} = 9.58 V, I{sub sc} = 52.0 mA, FF = 69.8%, and efficiency = 10.2%. A new version of EPV's linear evaporationmore » source was developed with improved rate and uniformity for Cu deposition over a width of 45 cm. Using the new linear source, the FORNAX process was implemented on 0.43-m{sub 2} substrates in EPV's CIGS pilot line, with V{sub oc} = 537 mV and FF = 70.3% being achieved on a device. The EPV Subteam of the National CIS R&D Team has produced Cd-free ZnO/CIGS devices on NREL CIGS using the ROMEAO process (reaction of metal and atomic oxygen) for ZnO deposition. After soaking, the best device exhibited a V{sub oc} of 565 mV and an efficiency of 12.3%. Novel bias drive methods were devised for field soaking/anti-soaking experiments as a function of time and temperature. Scaling laws and an activation energy of 0.51 eV were found. Thermally stimulated capacitance reveals the existence of three distinct contributions to ZnO/CIGS device capacitance, two appearing to be gap-state effects and one related to net doping concentration. The coating time of the sputtered pilot-line ZnO:Al has been reduced by a factor of 3 while maintaining film quality. The deposition rate is 48 A s{sup -1}. Plans are under way to increase the substrate size from 0.43 m{sup 2} to 0.79 m{sup 2}.« less

  • ; ; ; ...
    A summary of Energy Photovoltaics' Phase II work includes the following: (1) EPV has demonstrated that it can sputter a Mo back-contact capable of supporting very high efficiency cell processing. Using EPV Mo, NREL has deposited a 17.1% CIGS cell (no AR coating). EPV believes it can identify the signature of ``good'' Mo. The Mo was produced on EPV's 0.43 m{sup 2} pilot-line equipment; (2) EPV has performed compound synthesis for several classes of materials, namely non-Cu precursor materials, Cu-containing materials, and ternary buffer materials. Using a ternary compound synthesized at EPV (ZIS) as an evaporation source material for themore » buffer layer, a Cd-free CIGS device has been produced having an efficiency of 11.5% (560 mV, 32.1 mA/cm{sup 2}, FF 64.3%). The ZIS films are photoconductive, and the devices exhibit no dark-light crossover or light soaking effects; (3) EPV initiated the interest of the University of Oregon in capacitance spectroscopy of CIGS devices. An Urbach tail with characteristic energy E0 < 20meV was identified by transient photocapacitance spectroscopy; (4) Small-area CIGS devices were produced in the pilot-line system with an efficiency of 12.0% (581 mV, 30.1 mA/cm{sup 2}, FF 68.7%), and in an R and D-scale system with 13.3% efficiency (569 mV, 34.1 mA/cm{sup 2}, FF 68.1%); (5) An improved linear evaporation source for Cu delivery has been developed and was used for CIGS formation in the pilot-line system. The deposition width is 45 cm. This technological ``tour de force'' allows EPV to build large-area CIGS systems possessing considerable flexibility. In particular, both EPV's FORNAX process and NREL's 3-stage process have been implemented on the pilot line. A CIGS thickness uniformity of 7% over a 40 cm width has been achieved; (6) A 4-head linear source assembly was designed, constructed, and is in use. Flux monitoring is practiced; (7) Large-area CIGS modules were produced with Voc's up to 36.3 V; (8) EPV has started to construct an entirely new CIGS pilot line for scale-up and limited manufacturing purposes. The coating width will be 65 cm; (9) The company's analytical capabilities are currently being upgraded with the installation of ICP and SEM/EDS facilities.« less