CIGS电池效率20.3 % ZSW 记录保持者

EC y tte ichael Powalla n-W effi ch td. ors 1. INTRODUCTION research today. this contribution have an anti-reflective coating based on process flow, (2) use of clean materials, procedures and working environments, (3) variation of the selenium rate time. Figure 1 shows the I/V-curves and the electrical PROGRESS IN PHOTOVOLTAICS: RESEARCH AND APPLICATIONS Prog. Photovolt: Res. Appl. 2011; 19:894–897 Published online 5 January 2011 in Wiley Online Library (wileyonlinelibrary.com). DOI: 10.1002/pip.1078 Reference [3]. This means that special attention is paid to clean production environments and materials. Also very efficiencies from silicon solar cell efficiencies for a long efficiency line follows the same principles as described in 2. EXPERIMENTAL In order to pursue this goal, the ZSW has set up a specific high-efficiency small-area solar cell production line (measured cell area: 0.50 cm2) beside its pilot production line (30� 30 cm2 substrates). The concept of the high- 3. RESULTS We have been able, for the first time ever, to push CIGS efficiencies beyond 20%. This marks the breaking down of the barrier that has been separating thin-film solar cell and (4) fine-tuning of the cell stack. that for a real success of this new technology another boost from cost reduction and performance measures is vital. However, saved material costs very often cannot outweigh the negative impacts of such measures on device performance. Consequently, efficiency development has become one of the main focuses of the ZSW’s CIGS MgF2 (105 nm). Thus, a standard cell setup with standard procedures has been used. We define the cell size by mechanical scribing. The cell area equals 0.50 cm2 very reliably with very little variation. In order to achieve higher efficiencies, the following steps have been taken: (1) very strict standardisation of the the new solar spectrum to 20.0%). After the market introduction of CIGS technology [2], it became apparent laboratory environment was 19.9% [1] (corrected with 100 nm), sputtered aluminium doped ZnO (150–200 nm) and a nickel/aluminium-grid. All results presented in Only recently the highest efficiency obtained in a Cu(In,Ga)Se2 (CIGS) has gained a reputation as the thin-film solar cell technology with the highest efficiencies. and a highly standardised process sequence constitute this approach. The cell setup can be described as follows: soda-lime glass (3mm), sputtered molybdenum (500– 900 nm), CIGS (2.5–3.0mm), chemical bath deposited CdS buffer layer (40–50 nm), sputtered undoped ZnO (50– ABSTRACT In this contribution, we present a new certified world record cells. We analyse the characteristics of solar cells on su reproducibility. Copyright # 2011 John Wiley & Sons, L KEYWORDS Cu(In,Ga)Se2 (CIGS); record efficiency; thin-film solar cells *Correspondence Philip Jackson, Zentrum fuer Sonnenenergie- und Wasserstoff-F E-mail: philip.jackson@zsw-bw.de Received 7 May 2010; Revised 15 October 2010 PAPER PRESENTED AT 25th EU PVSEC WCP New world record efficienc solar cells beyond 20% Philip Jackson*, Dimitrios Hariskos, Erwin Lo Richard Menner, Wiltraud Wischmann and M Zentrum fuer Sonnenenergie- und Wasserstoff-Forschung, Bade short transfer times between the individual process steps 894 uerttemberg (ZSW), Germany ciency of 20.1 and 20.3% for Cu(In,Ga)Se2 thin-film solar a performance level and demonstrate a high degree of chung, Baden-Wuerttemberg (ZSW), Germany. -5, Valencia, Spain, 2010 for Cu(In,Ga)Se2 thin-film r, Stefan Paetel, Roland Wuerz, parameters of the new world record cells with 20.1 and Copyright � 2011 John Wiley & Sons, Ltd. Apart from this result, it is important to note that ese record cells are not single incidences but part of a igh-efficiency baseline. Figure 3 (baseline data up to pril 2010) shows the development of the baseline sults beyond 19%. A great number of over 180 cells ould reach or exceed an efficiency of 19.0%. The equency F of CIGS solar cells with efficiencies h equal or greater than the number stated in brackets is as llows: F(h� 19.0%)¼ 186, F(h� 19.5%)¼ 63, F(h� 9.9%)¼ 13, F(h� 20.0%)¼ 5 and F(h� 20.1%)¼ 4. hese results show a high degree of stability and producibility of the new high-efficiency baseline. From these results we have analysed the I/V- haracteristics of cells with an efficiency of 20% or etter in more detail as shown in Table I including the test 20.3% cell. The diode parameters as the shunt sistance rp, the series resistance rs, the saturation current ensity J0 and the ideality A are extracted from illuminated V-curves. Comparing the average values of the best Figure 1. I/V-curve of independently certified (by Fraunhofer ISE on 15th of April and 30th of June 2010) new world record cells of 20.1% (cell area: (0.5028�0.0015) cm2) and 20.3% (cell area: (0.5015� 0.0063) cm2) efficiency. P. Jackson et al. High efficiencies for Cu(In,Ga)Se2 20.3% efficiency, which were independently certified by Fraunhofer ISE. The external quantum efficiency (EQE) of these 20.1 and 20.3% efficient CIGS solar cell as depicted in Figure 2 show a very nice flat spectral response between 500 and 900 nm on a high level of approximately 90–95% (in particular for the 20.1% cell). The comparison with solar cells from the ipe as described in Reference [3] shows an improved collection between 750 and 1050 nm. A qualitative comparison with NREL’s 19.9% cell shows a slight superiority of our EQE between 550 and 1050 nm. Our cells show a higher open circuit voltage Voc than the optical band-gap derived from the EQE would suggest. This can be attributed to the compositional double-grading of the CIGS absorber (high Ga content at the front and at the back; low Ga content region near the front) which we normally see when employing our CIGS process. This grading separates the optical from the electrical band-gap. Figure 2. External quantum efficiency of the 20.1 and 20.3% record cells (measured by Fraunhofer ISE) and comparison to ipe results. Prog. Photovolt: Res. Appl. 2011; 19:894–897 � 2011 John Wiley & Sons, Ltd DOI: 10.1002/pip five of these cells with the 19.9% cell form NREL (Voc¼ 690mV, FF¼ 81.2%, Jsc¼ 35.5mA/cm2, J0¼ 2.1� 10�12 A/cm2, A¼ 1.14, rs¼ 0.37V cm2), we can see that our cells have a higher Voc (þ26mV), a lower FF (�3.2%), a higher Jsc (þ0.5mA/cm2), a higher J0 (by one to two orders of magnitude), a higher A (þ0.27) and a lower rs (�0.12V cm2). This comparison shows that there are still several paths to the 20% efficiency level for CIGS solar cells, which allows us to assume that there is still room for improvement even on this high performance level. These results are supported by Figures 4 and 5, which show the distribution of A and J0 for 64 CIGS cells with efficiencies equal to or greater than 19.5%. The average value for this big set of cells for A is 1.44. Most of the cells’ J0 values range between 1.4� 10�11 and 1.4� 10�10 A/cm2. Finally, we have analysed the correlation between the efficiency of the same set of 64 cells and their average composition determined by X-ray Fluorescence (XRF). Figure 3. High-efficiency baseline statistics: frequency F of CIGS solar cells with efficiencies equal to or greater than 19%: F(h� 19.0%)� 186, F(h� 19.5%)¼ 63, F(h� 19.9%)¼ 13, F(h�20.0%)¼ 5, and F(h�20.1%)¼ 4. th h A re c fr to fo 1 T re c b la re d I/ . 895 Table I. I/V-characteristics and diode analysis of one 20.3%, four 20 certified cells: no. Sample h (%) Voc (mV) FF (%) Jsc (mA/cm 2) J0 1 20.3 730 77.7 35.7 4 2 20.1 712 77.9 36.3 7 3 20.1 713 78.0 36.1 7 4 20.1 712 79.0 35.7 2 5 20.1 713 77.3 36.4 1 6 20.0 702 78.0 36.6 6 7 20.0 714 78.1 35.9 7 8 20.0 713 77.5 36.2 1 9 20.0 711 77.5 36.3 1 10 20.0 710 78.2 36.0 1 11 20.0 709 77.6 36.3 6 12 20.0 714 78.1 35.8 7 13 20.0 710 77.9 36.1 2 AVG 20.04 712 77.9 36.1 1 High efficiencies for Cu(In,Ga)Se2 P. Jackson et al. Figure 6 reveals that even on such a high efficiency level, the average composition is still a variable factor. This fact is one reason for the differences in the I/V characteristics between NREL’s and ZSW’s 20% CIGS cells. Figure 4. High-efficiency CIGS cells (N¼64 cells): ideality A varies around 1.44� 0.09. Figure 5. High-efficiency CIGS cells (N¼ 64 cells): most of the saturation current density values vary between 1.4� 10�11 and 1.4�10�10 A/cm2. 896 Prog. .1%, and eight 20.0% CIGS cells (all ‘in-house’ measurements/ 1 and no. 5). (A/cm2) A rs (V cm 2) rp (V cm 2) Jph (mA/cm 2) .2E-11 1.38 0.23 880 35.6 .6E-11 1.39 0.27 1755 36.2 .3E-11 1.39 0.27 1360 36.0 .9E-10 1.49 0.17 3095 35.6 .2E-10 1.42 0.30 1465 36.4 .8E-11 1.36 0.29 1605 36.6 .3E-11 1.39 0.29 1580 36.0 .3E-10 1.43 0.30 1680 36.0 .2E-10 1.42 0.49 1495 36.4 .3E-10 1.42 0.25 1565 36.0 .0E-11 1.37 0.42 1825 36.4 .2E-11 1.39 0.29 1505 35.8 .7E-10 1.48 0.42 2710 36.4 .2E-10 1.41 0.31 1732 36.1 4. CONCLUSION We have been able to surpass the 20% efficiency barrier for CIGS solar cells and have obtained a new world record efficiency of 20.1 and 20.3%. This record is the result of a highly stable and reproducible high-efficiency small-area CIGS solar cell production line. According to our own measurements, we have been able to reproduce these record values above 20% five times altogether. In addition, a significant number of 63 CIGS cells with efficiencies equal to or greater than 19.5% proves the remarkable reproducibility of this high performance level. Scientific literature shows that there are still many basic questions in CIGS research intensely debated (grain boundaries [4], sodium [5], inverted CIGS phase at surface [6–8], defects [9], etc.). At the same time CIGS technology, despite its meanwhile obvious progress in maturity, lacks Figure 6. High efficiencies and composition (average values derived from XRF measurements/compositional gradings not considered): big triangles represent the efficiency range 19.9%� h� 20.1%. Small circles represent the efficiency range 19.5%� h� 19.8%. CIGS solar cells on a 20% efficiency level can still be produced with varying composition (Ga/(Gaþ In) from 0.30 to 0.35 and Cu/(Gaþ In) ratio from 0.80 to 0.92). Photovolt: Res. Appl. 2011; 19:894–897 � 2011 John Wiley & Sons, Ltd. DOI: 10.1002/pip many of the refined performance boosting methods that have become a natural routine in silicon solar device production. These observations combined with the variable pathways to our new record efficiencies beyond 20% and that of NREL’s 20% cell lead us to the conclusion that there is a considerable performance potential still unexploited in CIGS solar technology. In the near future, this could signify thin-film CIGS technology not only as a low-cost alternative but also as a high-efficiency competitor on the photovoltaic world market. ACKNOWLEDGEMENTS The authors would like to thank the CIGS team at ZSW especially Dieter Richter and Wolfgang Dittus for the very valuable technical support in the laboratory. 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