epvfinal.docx

1、epvfinalENERGY PHOTOVOLTAICSThin-Film Photovoltaics Partnership ProgramAdvanced CIGS Photovoltaic TechnologyFinal Technical Report covering the periodNovember 15, 2001 February 13, 2005Subcontract No. ZDJ-2-30630-21underPrime Contract No. DE-AC36-99-GO10337Prepared by:A.E. Delahoy and L. ChenEnergy

2、Photovoltaics, Inc.P.O. Box 7456, Princeton, NJ 08543Submitted to:H.S. Ullal, Contract Technical Monitor National Renewable Energy Laboratory1617 Cole BoulevardGolden, CO 80401-3393February 28, 2005PrefaceTechnically, thin-film PV technologies have advanced considerably in the last few years. The le

3、ading thin film technologies are, broadly, a-Si (and variations), CdTe, CIGS, c-Si film, and dye-sensitized. At the time of writing, the leading commercially-available thin film technologies have demonstrated the following record aperture area efficiencies and powers for large area modules: CIGSS 13

4、.1% 64.8W Shell Solar GmbH (glass) CIGS 13.0% 84.6W Wrth Solar (glass) CdTe 10.2% 67.4W First Solar (glass) a-Si/c-Si 10.0% 38.0W Kaneka (glass) CIGS 10.1% 71.2W* Global Solar (ss) a-Si/a-SiGe/a-SiGe 7.6% 70.8W* United Solar (ss) CdTe 7.3% 52.3W Antec Solar (glass) a-Si 6.4% 100W Mitsubishi Heavy In

5、dustries (glass) a-Si/a-Si 6.1% 33.3W RWE (glass) a-Si 6.0% 48.6W Kaneka (glass) a-Si/a-si 5.8% 43.3W Energy Photovoltaics (glass) * assembly of cells (not monolithic) Even higher module efficiencies have been demonstrated by some companies that currently do not use the technology commercially, e.g.

6、 13.4% for CIGS by Showa Shell, and 11% for CdTe by BP Solar and Matsushita. Within each thin-film semiconductor technology category, various deposition methods have been devised, and many are represented in the above table. While a high module efficiency is desirable, module efficiency figures do n

7、ot tell the whole story. The long term commercial success of the various approaches is not automatically assured, but is dependent on a combination of module efficiency, manufacturing cost and market niche. For example, the manufacture of thin-film c-Si modules in the efficiency range 8-10% can be a

8、pproached by depositing and recrystallizing a-Si:H. Indeed, prototype modules have been produced and the process used has been described in the literature. It is instructive to analyze this thin-film c-Si process, and to compare it to CIGS processing. The analysis reveals more complex processing tha

9、n is required for CIGS (about 20 steps versus 12, exclusive of encapsulation), a high cost for the borosilicate glass, high capital costs, and extensive use of indirect materials in multiple etching processes. It is not clear that it offers a viable pathway to cost-effective manufacturing. Amorphous

10、 silicon, on the other hand, is of lower efficiency, but can be manufactured with high yield and at the lowest $/W of all the technologies mentioned. CIGS continues to hold the efficiency record, but the technology, although having entered the realm of manufacturing, is arguably not yet sufficiently

11、 evolved to be cost-competitive for production of standard power modules. One further factor that will eventually emerge as a strong driver of success for PV technologies in the energy market is the specific energy for module production. For PV to continue growing at 30% per year for the next 30 yea

12、rs so that it can take its place as a significant energy source on the world stage, modules will have to be made in a more energy-efficient manner. At this growth rate, for a new PV factory to generate a positive energy return in less than 10 years, the specific energy for module production must be

13、less than 18MJ/Wp 1. If a particular PV technology cannot meet this condition, it may be questioned whether large quantities of energy will in practice be expended to manufacture modules using such a technology. The published range of total energy requirements to produce wafer-based modules is 20-10

14、0 MJ/Wp. For a-Si the figure is 12-15MJ/Wp (EPV), while for CIGS the figure is 11MJ/Wp (Shell Solar).From the above discussion we see that the driving forces for CIGS are compelling: potentially high efficiency and low specific energy for production. To these we may add the broadly advantageous prop

15、erties of most thin-film PV processes relative to wafer-based PV: monolithic design and large substrates (leading to reduced parts handling), low consumption of both direct and indirect materials, and fewer process steps. Energy Photovoltaics, Inc. (“EPV”) is a solar energy company that primarily de

16、signs, develops, manufactures, and markets thin-film photovoltaic (PV) modules and Integrated Manufacturing Systems to serve the growing international PV marketplace. The strategy being pursued by EPV is premised on a fundamental belief that, for PV to be successful as more than a specialty source o

17、f electricity (with growth stimulated by government incentive programs), it must deliver electricity at the lowest possible cost. In this vein, EPV continues to ship its EPV-40 tandem junction, amorphous silicon PV modules manufactured at its headquarters in Lawrenceville, NJ. The modules are UL-lis

18、ted and have IEC 61646 certification. The production is fully sold out for 2005. On the IMS front, EPV completed a 2.5MW a-Si module manufacturing plant for the Tianjin Jinneng Solar Cell Corp. in China in April 2004. The plant met all production rate and quality deliverables and is in full producti

19、on. EPV is also supplying an a-Si IMS rated at 11MW to Heliodomi, S.A. of Thessaloniki, Greece. In parallel with a-Si production, Energy Photovoltaics, Inc. is also developing technology to be able to cost-effectively manufacture much higher efficiency CIGS modules. EPV has consistently pursued a va

20、cuum-based approach to CIGS production, and has developed novel linear thermal source technology to supply materials to heated, moving, soda-lime glass substrates. It has also deliberately chosen to develop processing methods with worker safety in mind. These strategically-important choices offer a

21、low-cost substrate, control over layer homogeneity and purity, and production without significant hazards. Although such approaches help to minimize the processing costs of CIGS, further advances appeared necessary in order to improve both ease of production and yield. One such advance, the introduc

22、tion of Cu sputtering, was accomplished under the NREL Thin-Film Photovoltaics Partnerships Program (TFPPP). To facilitate the development of CIGS, CdTe, and Si-based thin-film technologies, NREL operates the Thin-Film Photovoltaics Partnerships Program. The long-term objective of the TFPPP is to de

23、monstrate commercial, low-cost, reproducible modules of 15% aperture-area efficiency 2. As a Technology Partner within this program, EPV has performed research under a three-phase, cost-shared subcontract entitled “Advanced CIGS Photovoltaic Technology” and participates in the National CIS Team Meet

24、ings. One of the main objectives of this subcontract (RDJ-2-30630-21) was for EPV to demonstrate its capability to produce reasonably efficient CIGS modules at a substrate size of 4300 cm2. The processing also needed to be reproducible with good controllability. This goal was successfully accomplish

25、ed by the development and utilization of a new hybrid process for CIGS growth during the three year contract period. This final technical report mentions highlights of the first and second phases of the subcontract, and describes in detail results obtained during the third phase of the subcontract.T

26、he benefits accruing from the hybrid process raises the obvious question of whether process and equipment development does more to advance PV technology than the more traditional research into materials and devices. CONTENTSPreface iiTable of Contents vList of Tables . viList of Figures . vi1.0 Intr

27、oduction . 12.0 Highlights of Phases I and II. 23.0 CIGS Optimization and Device Results 3 3.1 Composition and Cu rich regime 3 3.2 Selenization temperature 43.3 Ga distribution and bandgap profile. 53.4 Other parameters. 53.5 Device performance 5 4.0 CIGS Film Analysis. 6 4.1 Scanning electron micr

28、oscopy . 64.2 Depth profiling by Auger electron spectroscopy . 7 4.3 X-ray diffraction. 8 4.4 Activation energy. 9 5.0 Full Size Module Process and Performance . 9 5.1 CBD CdS made in full size tank. 9 5.2 Investigation of contact resistance between ZnO and Mo. 10 5.3 Uniformity improvement for larg

29、e area plates. 11 5.4 Module performance. 15 5.5 Long-term stability of EPV module. 16 5.6 Process control and database. 17 6.0 Surface Treatment. 177.0 Development of New TCO Window Layers. 188.0 Future Work. 19 9.0 Phase III Summary . 20 Acknowledgments. 21References. 22TABLESTable 3.1. Deposition

30、 conditions and resulting composition and device performanceTable 5.1. Device FF mapping to compare beaker and tank CBD processTable 5.2. Transmission distribution (at 420 nm) of CTO glass coated with CdS filmTable 5.3. Performance of modules made during the Final PhaseTable 6.0. Device performance with various surface treatmentsTable 7.0. Properties of TCO films made by RE-HCSTable 7.1. J