This paper discusses the developments in thin-film PV technologies and provides an outlook on future commercial module efficiencies achievable based on today's knowledge about champion cell performance

Ullal, H. S.

von Roedern, B.

UNT Digital Library

 A national laboratory of the U.S. Department of EnergyOffice of Energy Efficiency & Renewable EnergyNational Renewable Energy Laboratory Innovation for Our Energy Future The Role of Polycrystalline  Thin-Film PV Technologies in Competitive PV Module Markets Preprint  B. von Roedern and H.S. Ullal National Renewable Energy Laboratory Presented at the 33rd IEEE Photovoltaic Specialists Conference San Diego, California May 11–16, 2008 Conference Paper NREL/CP-520-42494 May 2008 NREL is operated by Midwest Research Institute ● Battelle     Contract No. DE-AC36-99-GO10337  NOTICE The submitted manuscript has been offered by an employee of the Midwest Research Institute (MRI), a contractor of the US Government under Contract No. DE-AC36-99GO10337. Accordingly, the US Government and MRI retain a nonexclusive royalty-free license to publish or reproduce the published form of this contribution, or allow others to do so, for US Government purposes. This report was prepared as an account of work sponsored by an agency of the United States government. Neither the United States government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights.  Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States government or any agency thereof.  The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States government or any agency thereof. Available electronically at http://www.osti.gov/bridge Available for a processing fee to U.S. Department of Energy and its contractors, in paper, from: U.S. Department of Energy Office of Scientific and Technical Information P.O. Box 62 Oak Ridge, TN 37831-0062 phone:  865.576.8401 fax: 865.576.5728 email:  mailto:reports@adonis.osti.gov Available for sale to the public, in paper, from: U.S. Department of Commerce National Technical Information Service 5285 Port Royal Road Springfield, VA 22161 phone:  800.553.6847 fax:  703.605.6900 email: orders@ntis.fedworld.gov online ordering:  http://www.ntis.gov/ordering.htm Printed on paper containing at least 50% wastepaper, including 20% postconsumer waste The Role of Polycrystalline Thin-Film PV Technologies in  Competitive PV Module Markets  Bolko von Roedern and Harin S. Ullal National Center for Photovoltaics, National Renewable Energy Laboratory 1617 Cole Boulevard, Golden, CO 80401-3393 USA    ABSTRACT  This paper discusses the developments in thin-film PV technologies.  It provides an outlook on future commercial module efficiencies achievable based on today’s knowledge about champion cell performance.  It also provides a relative cost comparison of thin-film and wafer/ribbon based Si PV modules.  In 2007, about 65% of the modules produced in the US were thin-film modules when amorphous silicon modules are also considered.   INTRODUCTION  This paper updates a methodology presented at the 31st IEEE PVSC Conference (2005) [1].  Different PV flat-plate technologies are compared on the basis of verified champion cell efficiencies; projections are made for commercial module efficiencies estimating that they will be proportional  to verified best solar cell efficiencies.  We will also review the technical issues affecting performance and commercialization of polycrystalline thin film PV modules.   We update our semi-empirical methodology of comparing verified stabilized best or “champion” solar cell data with performance achieved on commercial manufacturing lines [2], estimating the performance and cost developments for future successful PV module candidates. Table 1 is compiled from a survey of manufacturer’s websites in April 2008. The  5th column in Table  1 indicates the c/c ratio, i.e.,  the ratio of respective module and best cell efficiency, where cell numbers given in Ref. 2 are used.  Table 1: Module Efficiency from survey of manufacturers’ websites and “Performance Ratios [3]”  Eff. (%) Module  T.coeff. (power) Technology Current c/c performanceratio cell/module 19.3 SunPower 315 -0.38 %/C mono-Si, special junction (sp. j.) 78% 17.4 Sanyo HIP-205BAE -0.30 %/C CZ-Si, “HIT,” sp. j. 70% 15.1 BP7190 -0.5 %/C CZ-Si, sp. j. 61% 14.2 Kyocera KC200GHT-2 n/a MC-Si, standard junction (std. j.) 70% 14.2 Solar World SW 185 n/a CZ-Si, std. j. 70% 14.2 BP SX3200 -0.5 %/C MC-Si, std. j. 70% 13.4 Suntech STP 260S-24V/b n/a MC or CZ-Si, std. j. 66% 13.4 Solar World SW 225 n/a MC-Si, std. j. 66% 13.1 Evergreen Solar ES 195 (up to)-0.5%/C String-ribbon-Si std. j. 65% 11.0 WürthSolar WS11007/80 -0.36%/C CIGS 55% 10.4 First Solar FS-275 -0.25%/C CdTe 63%  8.5 Sharp NA-901-WP -0.24%/C a-Si/nc-Si 70%  8.1 GSE Solar GSE120-W -0.5%/C CIGS 41%  6.3 Mitsubishi Heavy MA100 -0.2 %/C a-Si, single-junction  66%  6.3 Uni-Solar PVL136 -0.21 %/C a-Si, triple junction 52% 6.3 Kaneka T-SC(EC)-120 n/a a-Si single junction 66% 5.9 Schott Solar ASI-TM86 -0.20%/C a-Si/a-Si same bangdgap tandem 62% 5.3 EPV EPV-42 -0.19%/C a-Si/a-Si same bandgap tandem 56%  1 In Table 2, we have listed expected future commercial module performance, multiplying current best cell performance by 0.8 (i.e., taking the future c/c ratio as 0.8 for all PV technologies) [4].  Future relative module performance was calculated by dividing future module efficiencies by the future standard Silicon efficiency number, because “standard Si” currently constitutes the prevailing PV technology (“standard Si” refers to cells fabricated by diffusion and screen printing processes).  The last column of the table shows 1/relative-performance, if thin-film technology, hence avoiding the use of Si wafers, multiplied by 0.5 (the thin-film PV “advantage factor”).  Anything in this column with a number <1 should show a manufacturing cost advantage over standard silicon.  Manufacturing detail and cost control will affect the actual values, but the strength of our approach is to apply the same methodology to different flat-plate PV technologies.  Compared to our last paper [1], we have increased the cost advantage of thin film modules over wafer Si modules from 40% to 50%.  In the past, Si feedstock and wafer costs were largely determined using ‘second-grade’ electronic poly-Si feedstock, that may have established cost figures for wafers made from feedstock acquired below cost. Current analysis by Rogol indicates wafer cost to constitute about 60% of the cost of a wafer Si module [5]. Converting the cost figures into percentages (wafer-cost/module-cost) it is apparent that currently such percentage is near 60%; therefore,  it appears likely that wafer costs could still make up approximately 50% of the cost of a crystalline Si PV module in years to come.   Table 2:  Anticipated Future Module Efficiency and Relative Cost Based on  Today’s Demonstrated   Champion Cell Performance  Technology Future commercial module performance (80% of current record cell efficiency) Future Relative Performance  Future Relative-cost (using a 50% thin film PV advantage) Silicon (non-stand) 19.8% 1.18 0.85 (competitive) Silicon (standard) 17.0% 1.00 1.00 (reference) CIS 15.9% 0.92 0.54 (highly competitive) CdTe 13.2% 0.78 0.64 (highly competitive) a-Si (1-j) 8.0% 0.47 1.06 (about the same) a-Si (3-jj), (or a-Si/nc-Si) 9.7% 0.57 0.88 (competitive)   It should be noted that in order to attain the relative cost given in the 4th column of Table 2, module efficiencies given in column 2 will have to be achieved.  As can be seen from the 5th column of Table 1, many PV manufacturing schemes still show a c/c-ratio well below the value of 80% assumed for the data in Table 2, indicating that some progress with product performance is possible due to implementing better manufacturing methods.    RESEARCH AND DEVELOPMENT ISSUES  Our analysis above shows that module performance remains a significant factor for determining module cost.   Since solar cell processing is often found to affect cell efficiency, it is important to assess (a) the true advantage of each process, and (b)  how it can be handled in a manufacturing environment.  It is also desirable to develop greater confidence and insight when chosen processes can be improved further by optimization, and when processes should be substituted or added.   In case of the CIS PV technology, manufacturing scale up issues have frequently prevented companies from successfully  using  high efficiency cell recipes for commercial production of modules with commensurate efficiency.  This technology is in need to better understand the effects of deposition processes, choice of cell structures, and deposition rates on cell and module performance and device stability.  In case of CdTe modules, development of improved device schemes that lead to high performance, low manufacturing cost, and good device stability have to be investigated. Since 2006, DOE’s new program to assist the development and deployment of photovoltaic technology, the Solar America Initiative (SAI) provides the means of developing PV technologies and advance PV manufacturing.   Programs of interest to cell and module manufacturing include the Technology Pathway Partnership, TPP, geared towards larger and more mature entities, the PV Incubator program for small businesses, as well as the Future Generation and University programs geared at longer-term technology developments or in support of university driven R&D aspects, respectively.  Among different PV technologies, the following thin-film PV companies are being supported: Uni-Solar (a-Si), and Nanosolar (CIGS) obtained TPP awards, and AVA Solar (CdTe), Primestar Solar (CdTe), SoloPower (CIGS), and Blue Square Energy (Si film) received SAI PV Incubator awards.     2COMMERCIAL STATUS OF THIN-FILM PV  It seems reasonable from time to time to assess the impact of R&D developments on actual commercial product.  In Fig. 1, we show the progress, broken down by technology, by averaging by technology best commercial module efficiencies as shown in Table 1 (such data have been compiled since 04/2004) [6]. For this period considered, the most impressive progress in module efficiency has been obtained for the CdTe technology by First Solar. 2007 has been considered a turning point for thin film PV at least for US-based PV manufacturing, with US thin-film shipments reaching a market share of about 65% [7].  First Solar and United Solar Ovonic became the number 1 and number 2 ranked US manufacturers, respectively.  Using the breakdown provided by PV News [7], and only counting the thin-film PV “pure play” entities First Solar, United Solar, and Global Solar in the thin-film category (there may be a small amount of thin film PV within the “others” category, which constitutes largely wafer/ribbon Si flat plate technologies), we compiled Fig. 2.  Estimates for 2008 production are taken as 2/3 of the PV News published capacity numbers for 2008.  Projections for 2009 and beyond are currently difficult, because it is not known where in the world companies will expand manufacturing and when exactly some announced large capacities will come on line.  Given the size of some announcements, even a 3-month delay in getting such factory to produce at capacity could make a significant difference in the amounts produced.  Currently, First Solar has announced capacity expansion greater than 1000 MWp annual capacity by the end of 2009, but those new factories are built (already under construction) in Malaysia.    Fig 1: Development of Commercial Module Efficiency, from survey of manufacturers’ websites,  broken down by PV Technology   3 US Produced PV Shipments  Fig 2: US produced Modules thru 2007, counting First Solar, Uni-Solar and Global Solar as “thin Film” PV and the rest as “other.” Projections for 2008 use 2/3 of PV News reported end of 2008 capacity figures.   ACKNOWLEDGEMENT  This work was supported by the U.S. Department of Energy under Contract No. DEAC36-99GO10337 with the National Renewable Energy Laboratory. We would like to thank many colleagues in the PV field for fruitful interactions.  REFERENCES  [1] Bolko von Roedern, Harin S. Ullal, and Ken Zweibel, ‘Polycrystalline Thin-Film Photovoltaics: From the Laboratory to Solar Fields,’ Proc. 31st IEEE PVSC (2005), p. 183.  [2] Martin A. Green, Keith Emery, Yoshihiro Hishikawa and Wilhelm Warta ,  “Solar Cell Efficiency Tables (Version 31),” Prog. Photovolt: Res. Appl. 2008; 16:61–67    [3] Some of the manufacturer’s spec sheet websites are given below.  Note that product specifications can change, including the possibility of new modules becoming available or discontinuation of certain models.  [4] Bolko von Roedern, refocus magazine, (July + August 2006) p. 34.  [5] Michael Rogol, “Refining Benchmarks and Forecasts – Rogol’s Monthly Market Commentary,” Photon International, Jan. 2008, 84  [6] Older module specification sheets can currently be found on the NREL website http://www.nrel.gov/ by searching for it “spec sheet.”  [7] PV News, Greentech Media and Prometheus Institute, 03/2008 issue    4F1147-E(09/2007) REPORT DOCUMENTATION PAGE Form Approved OMB No. 0704-0188 The public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing the burden, to Department of Defense, Executive Services and Communications Directorate (0704-0188). Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ORGANIZATION. 1. REPORT DATE (DD-MM-YYYY) May 2008 2. REPORT TYPE Conference Paper 3. DATES COVERED (From - To)  5a. CONTRACT NUMBER DE-AC36-99-GO10337 5b. GRANT NUMBER  4. TITLE AND SUBTITLE The Role of Polycrystalline Thin-Film PV Technologies in Competitive PV Module Markets: Preprint 5c. PROGRAM ELEMENT NUMBER  5d. PROJECT NUMBER NREL/CP-520-42494 5e. TASK NUMBER PVB75401 6. AUTHOR(S) B. von Roedern and H.S. Ullal 5f. WORK UNIT NUMBER  7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) National Renewable Energy Laboratory 1617 Cole Blvd. Golden, CO 80401-3393 8. PERFORMING ORGANIZATION REPORT NUMBER NREL/CP-520-42494 10. SPONSOR/MONITOR'S ACRONYM(S) NREL 9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES)  11. SPONSORING/MONITORING AGENCY REPORT NUMBER  12. DISTRIBUTION AVAILABILITY STATEMENT National Technical Information Service U.S. Department of Commerce 5285 Port Royal Road Springfield, VA 22161 13. SUPPLEMENTARY NOTES  14. ABSTRACT (Maximum 200 Words) This paper discusses the developments in thin-film PV technologies.  It provides an outlook on future commercial module efficiencies achievable based on today’s knowledge about champion cell performance.  It also provides a relative cost comparison of thin-film and wafer/ribbon based Si PV modules.  In 2007, about 65% of the modules produced in the US were thin-film modules when amorphous silicon modules are also considered. 15. SUBJECT TERMS PV; polycrystalline; thin film; module; wafer; ribbon based; amorphous silicon; champion cell efficiency 16. SECURITY CLASSIFICATION OF: 19a. NAME OF RESPONSIBLE PERSON  a. REPORT Unclassified b. ABSTRACT Unclassified c. 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Role of Polycrystalline Thin-Film PV Technologies in Competitive PV Module Markets: Preprint

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Role of Polycrystalline Thin-Film PV Technologies in Competitive PV Module Markets: Preprint

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