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Data of ALD Al2O3 rear surface passivation, Al2O3 PERC cell performance, and cell efficiency loss mechanisms of Al2O3 PERC cell
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Data Article
Data of ALD Al2O3 rear surface passivation, Al2O3 PERC cell performance, and cell efficiency loss mechanisms of Al2O3 PERC cell Haibing Huang a,b,n, Jun Lv a, Yameng Bao b, Rongwei Xuan a, Shenghua Sun a, Sami Sneck c, Shuo Li b, Chiara Modanese b, Hele Savin b, Aihua Wang a, Jianhua Zhao a a
China Sunergy, No.123. Focheng West Road, Jiangning Zone, Nanjing, Jiangsu 211100, China Aalto University, Department of Micro and Nanosciences, Tietotie 3, Espoo 02150, Finland c Beneq Oy, P.O. Box 262, Vantaa 01511 , Finland b
a r t i c l e i n f o
abstract
Article history: Received 21 November 2016 Received in revised form 13 December 2016 Accepted 15 December 2016
This data article is related to the recently published article ‘20.8% industrial PERC solar cell: ALD Al2O3 rear surface passivation, efficiency loss mechanisms analysis and roadmap to 24%’ (Huang et al., 2017) [1]. This paper is about passivated emitter and rear cell (PERC) structures and it describes the quality of the Al2O3 rear-surface passivation layer deposited by atomic layer deposition (ALD), in relation to the processing parameters (e.g. pre-clean treatment, deposition temperature, growth per cycle, and film thickness) and to the cell efficiency loss mechanisms. This dataset is made public in order to contribute to the limited available public data on industrial PERC cells, to be used by other researchers. & 2016 Published by Elsevier Inc. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
n
DOI of original article: http://dx.doi.org/10.1016/j.solmat.2016.11.018 Corresponding author at: China Sunergy, No.123. Focheng West Road, Jiangning Zone, Nanjing, Jiangsu 211100, China. E-mail address: [email protected] (H. Huang).
http://dx.doi.org/10.1016/j.dib.2016.12.030 2352-3409/& 2016 Published by Elsevier Inc. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
Please cite this article as: H. Huang, et al., Data of ALD Al2O3 rear surface passivation, Al2O3 PERC cell performance, and cell efficiency loss mechanisms of Al2O3 PERC cell, Data in Brief (2016), http: //dx.doi.org/10.1016/j.dib.2016.12.030i
H. Huang et al. / Data in Brief ∎ (∎∎∎∎) ∎∎∎–∎∎∎
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55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108
Specifications Table Subject area More specific subject area Type of data How data was acquired
Data format Experimental factors
Experimental features
Data source location
Data accessibility
Physics Silicon solar cells, device simulations Figures, tables, graphs, spectra Effective minority carrier lifetime, implied Voc, pseudo I-V and illuminationVoc curves by Sinton WCT-120 Suns-Voc tester [2]; I-V curves and cell performances of the Si solar cell by HALM I-V tester or at Fraunhofer ISE; Thickness and refractive index of dielectric films by Suntech ellipsometer; Fixed negative charges (Qf) and interface defect density (Dit) by Semilab SDI PV2000 [3]; Cross-sectional EDS analysis with Vantage-100 EDS instrument from Thermo Electron Corporation; Silicon solar cell series resistance components calculated using Meier's method[4]; Resistance in the sub-cell array measured by grid resistance tester; Contact resistance measured by grid resistance tester based on the transmission line model [5]. Raw and analyzed The wafer samples for lifetime, film thickness, refractive index, Qf, and Dit were treated in NaOH solution to remove saw damage and cleaned in HCl and HF before the ALD Al2O3 process. PERC cells were processed from B-doped, Czochralski-grown, pseudo-square, 6″ wafers with 190 mm thickness. The processing flow is: saw damage removal (NaOH) with random-pyramid texturing, POCl3 diffusion (front n þ emitter, 90 Ω/□ sheet resistance), edge isolation with rear side polishing (HNO3–HF– H2SO4 solution), ALD Al2O3 and PECVD SiNx rear side passivation stacks, local patterning with laser ablation (532 nm, ps-laser), screen printing and cofiring for front (Ag/n þ –Si ohmic contact) and rear side metallization (Al local back surface field and local Al/p þ –Si Ohmic contact). For cell measurements, the completed solar cells were tested before lightinduced degradation after storage in a nitrogen gas cabinet. Cross-sectional SEM/EDS analysis on the local Al–Si rear contact areas was done on three cross sections along the (110) crystallographic orientation with an angle of 45° with respect to the local line contacts at the rear. The focus is on ozone (O3) and Al(CH3)3 trimethylaluminium (TMA) based thermal ALD process, implemented by Beneq's industrial P800 batch ALD tool. Temperature is 200 °C, Al2O3/SiNx thickness ratio is 10 nm/100 nm, deposition pressure is 150–500 Pa, rapid thermal processing (RTP) firing is at 760 °C peak temperature in compressed air for 2–3 s. The effective minority carrier lifetime and implied Voc measurements were carried out with the generalized mode, 5 1015 cm 3 injection level and optical constant of 0.7 for Si (100) surfaces and 0.85–0.95 for Al2O3/SiNx stack. ALD Al2O3 process pressure and post-ALD anneal temperature and time were monitored by the process tool. (1) China Sunergy, No.123. Focheng West Road, Jiangning Zone, Nanjing, Jiangsu, 211100, China (2) Aalto University, Department of Micro and Nanosciences, Tietotie 3, 02150 Espoo, Finland Data is within this article and in Ref. [1]
Please cite this article as: H. Huang, et al., Data of ALD Al2O3 rear surface passivation, Al2O3 PERC cell performance, and cell efficiency loss mechanisms of Al2O3 PERC cell, Data in Brief (2016), http: //dx.doi.org/10.1016/j.dib.2016.12.030i
H. Huang et al. / Data in Brief ∎ (∎∎∎∎) ∎∎∎–∎∎∎
Value of the data
The data on the quality of the atomic layer deposition (ALD) Al2O3 rear surface passivation and on
front Ag metallization pattern design provides a valuable dataset on the current industrial PERC structure and potentials, which can be used by researchers for the optimization of the current cell processes. The interplay between different parameters provides an overall description of the Al2O3 rear surface passivation process which leads to the optimal final passivation quality. The analysis on the loss mechanisms gives a relevant indication of the relative importance of different processing parameters via the calculation of the series resistance for the various components of the PERC cell. The data presented is collected from an extensive database from industrial PERC cells, and can thus be used by other researchers as a benchmark for industrial performances.
1. Data The dataset of this paper provides additional information to Ref. [1]. The rear surface passivation quality in relation to the ALD Al2O3 processing parameters is reported in Figs. 1–5, the PERC cell properties are reported in Figs. 6–8 and Table 1, and the metal contact design pattern and parameters are reported in Table 2.
2. Experimental design, materials and methods The procedure prior to the minority carrier lifetime measurements on the ALD Al2O3 rear surface passivation is described in detail in Fig. 1 in Ref. [1] and the most relevant aspects are reported here. All samples underwent saw damage removal and pre-ALD clean, followed by ALD Al2O3 deposition with varying parameters. Post-ALD anneal was performed on most of the samples, and then followed by plasma enhanced chemical vapor deposition (PECVD) of the SiNx capping layer. Afterwards, since lifetime cannot be measured after metallization, the samples were divided into two groups; one group directly underwent rapid thermal processing (RTP) firing, whereas a second group first underwent screen-printing of Al paste, then RTP firing followed by Al paste removal. All the samples were then measured under similar parameters. The interface defect density (Dit), the negative fixed charges (Q f) and open circuit voltage (Voc) as a function of the pre-ALD clean parameters are reported in Fig. 1. SC1 and SC2 pre-clean can achieve the best passivation quality (both regarding Dit and Voc). The pre-ALD clean does not affect the amount of Q f. Note that in the industrial PERC cell process, edge isolation and rear side polishing prior to the Al2O3 process normally terminate with HCl–HF clean sub-step.
Dit Qf
2.5x1011 2.0x1011
-2.0x1012
1.5x1011 1.0x10
Avg. Voc Best Voc
662
-1.5x1012 Voc (mV)
Dit at midgap(cm-2ev-1)
664
-1.0x1012
3.0x1011
Qf (cm-2)
109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162
3
660
-2.5x1012
658
-3.0x1012
656
11
No pre-clean
HCl-HF
HF-SC1-SC2-HF
Pre-ALD clean process
2-HF HCl-HF HF-SC1-SC Pre-ALD clean process
Fig. 1. Dit and Q f (a) and Voc (b) as a function of pre-ALD clean for Al2O3 passivation.
Please cite this article as: H. Huang, et al., Data of ALD Al2O3 rear surface passivation, Al2O3 PERC cell performance, and cell efficiency loss mechanisms of Al2O3 PERC cell, Data in Brief (2016), http: //dx.doi.org/10.1016/j.dib.2016.12.030i
H. Huang et al. / Data in Brief ∎ (∎∎∎∎) ∎∎∎–∎∎∎
4
After Firing
After Al paste removal
700
20.6
660
600
400 300
656 20.2
ηcell (%)
20.4
500
Voc (mV)
Effective minority lifetime(μs)
652
200
20.0
100 0
19.8
648 160
200
240
275
160
ALD Process Temperature (°C)
200
240
275
ALD Process Temperature (°C)
Fig. 2. Effective minority carrier lifetime (a) and cell performance (b) as a function of ALD temperature for Al2O3 passivation.
1.05
1.64 1.62
1.00
1.60 0.95 ALD growth rate Refractive index 0.90
160
200
240
Refractive index
ALD growth rate ( /cycle)
163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216
1.58 275
ALD process temperature (°C) Fig. 3. Growth rate (Å/cycle) and refractive index as a function of ALD process temperature.
The effect of the ALD process temperature for Al2O3 passivation on effective minority carrier lifetime and PERC cell performance (as Voc and cell efficiency (ηcell)) is reported in Fig. 2, while the effect on growth rate and refractive index (nk) of the dielectric layer is shown in Fig. 3. Our data show that the optimal temperature for passivation (in relation to both the effective lifetime and ηcell) is in the range of 200–240 °C, whereas the passivation level drops sharply at 275 °C. Note also that the process window between 160 and 240 °C is broad. In addition, the growth rate begins to decrease for temperatures above 200 °C. The refractive index is relatively low below 200 °C (nk ¼1.57), and it is stable (nk ¼1.63–1.65) between 200 and 400 °C. The optimal temperature for growth rate and refractive index is also around 200 °C. Fig. 4 shows the passivation quality as effective minority carrier lifetime, PERC cell performance (Voc and ηcell), Dit and Qf as a function of the Al2O3 film thickness. Effective minority lifetime and cell performance gradually increase with thickness increasing from 3.5 to 16 nm, where the optimal thickness is 10 nm. When the film thickness increases from 3.5 to 16 nm, cell performances and Dit gradually improve, while Qf is at the same level. Note that even a thin Al2O3 film of about 3.5 nm can work well on PERC cell (Voc E652 mV and ηcell E20.3%). SEM/energy dispersive X-ray spectroscopy (EDS) analysis on the effect of voids on the local back surface field (LBSF) rear local contact was performed and is shown in Fig. 5. Note that the spectra in the figure are from the Al-Si eutectic, the Al LBSF and the Si substrate, respectively. The detailed interpretation of the differences among the spectra is given in Ref. [1]. The thickness of the Al LBSF layer is 10 μm, thus revealing that the junction depth is deeper than 10 μm. Representative examples of industrial PERC cell performances are reported in Figs. 6,7. The certified current-voltage (I-V) curve and cell performance of one SiO 2 -PERC cell was measured at Please cite this article as: H. Huang, et al., Data of ALD Al2O3 rear surface passivation, Al2O3 PERC cell performance, and cell efficiency loss mechanisms of Al2O3 PERC cell, Data in Brief (2016), http: //dx.doi.org/10.1016/j.dib.2016.12.030i
H. Huang et al. / Data in Brief ∎ (∎∎∎∎) ∎∎∎–∎∎∎
Avg. V
Best T
800
Avg. η
Best V
Best η
20.7
660 658
20.6
Voc (mV)
600
400
656 20.5 654 20.4
652
200
20.3
650 6 nm
11 nm
16 nm
3.5 nm
Al2O3 film thickness (nm)
11 nm
16 nm
Al2O3 film thickness (nm)
11
0 Dit
-1
Dit at midgap ( cm ev )
6x10
6 nm
-2
Qf 4x1011
-1x10
12
2x1011
-2x10
12
0
Qf(cm-2)
3.5 nm
ηcell (%)
Avg. T Effective minority lifetime (μs)
217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270
5
-3x1012 3.5 nm
6 nm
11 nm
16 nm
Al2O3 film thickness (nm) Fig. 4. Effective minority carrier lifetime (a), Voc and ηcell (b), Dit and Qf (c) as a function of Al2O3 film thickness for Al2O3 passivation.
Fig. 5. Cross-sectional EDS analysis of the Al-Si contact areas (Fig. 14-c and Table 4 in Ref. [1]). Here, point 1 (pt1): Al-Si alloy, point 2 (pt2): Al LBSF, and point 3 (pt3): Si substrate.
Fraunhofer ISE in July 2013 under standard test conditions (see Fig. 6). Note that the key process in this structure is rear surface passivation with thermal oxidation and dielectric opening with Merck's chemical paste. Fig. 7 shows a typical example of the cell efficiency of an average
Please cite this article as: H. Huang, et al., Data of ALD Al2O3 rear surface passivation, Al2O3 PERC cell performance, and cell efficiency loss mechanisms of Al2O3 PERC cell, Data in Brief (2016), http: //dx.doi.org/10.1016/j.dib.2016.12.030i
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Fig. 6. Cell performance and I-V curve of one SiO2-PERC cell example (before light induced degradation) tested by Fraunhofer ISE in July 2013 (under Standard Test Condition of global AM1.5, 1000 W m 2, 25 °C).
Ncell Avg. cell efficiency: 20.22%
21.0 20.5
Ncell (%)
20.0 19.5 19.0 18.5 18.0 0
250
500
750 1000 1250 1500 1750 2000
Cell No. Fig. 7. The scatter diagram of the industrial Al2O3 PERC cell performance ( 2000 PERC cells/batch, before light induced degradation).
Voltage (V)
Measured Suns-Voc
10.000 Illumination (Suns)
Pseudo Light IV curve without the effect of Rs 0.045 0.028 0.04 0.035 0.03 0.019 0.025 0.02 0.015 0.009 0.01 0.005 0 0.000 0.00 0.20 0.40 0.60 0.80
Power Density (W/cm2)
Current (A/cm2)
271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324
Double Diode Fit
1.000 0.100 0.010 0.001 0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
Open Circuit Voltage (Volts)
Fig. 8. Suns-Voc measurement of the PERC cell sample A (Table 5 in Ref. [1]): pseudo I-V curve (left) and illumination-Voc (right).
Please cite this article as: H. Huang, et al., Data of ALD Al2O3 rear surface passivation, Al2O3 PERC cell performance, and cell efficiency loss mechanisms of Al2O3 PERC cell, Data in Brief (2016), http: //dx.doi.org/10.1016/j.dib.2016.12.030i
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325 Table 1 326 Q2 The calculation of series resistance of the industrial Al2O3 PERC cell using Meier's method [4]. 327 Description Key measurement Specific resisresistance Fraction 328 tance (Ω cm2) (mΩ) 329 Item Measured value 330 1. Front Ag busbar Resistance length 0.098 0.0073 0.0299 1.22% 331 of busbar 332 2. Rear AgAl busbar Similar to front estimated 0.0040 0.0165 0.67% 333 busbar 3. Front Ag grid Busbar-to-busbar 0.055 Ω 0.2197 0.9070 36.82% 334 resistance 335 0.009 Ω/□ 0.0419 0.1730 7.02% 4. Rear Al metallization Rsheet_metal 336 5. Front n þ emitter Rsheet_emitter 90 Ω/□ 0.1971 0.8137 33.03% 337 6. Rear Si substrate lateral Rsheet_Si substrate 121 Ω/□ 0.0746 0.3081 12.51% 338 spreading resistance 0.0161 0.0665 2.70% 7. Front Ag/n–Si contact TLM measurement Specific contact resis339 [5] tance: 3.1 mΩ cm2 340 8. Rear Al/p–Si contact TLM measurement Specific contact resis0.0030 0.0124 0.50% 341 [5] tance, estimated 342 9. p–Si substrate Resistivity, thick2 Ω cm, 165 μm 0.0330 0.1362 5.53% ness of wafer 343 – – 0.5967 2.4635 100% Rs-Total 344 345 346 347 348 Table 2 The basic information of the design pattern of the front Ag contact of the Al2O3 industrial PERC cell in this data article. 349 350 Key parameters Description Value 351 352 n-front Ag the number of front grid 96 b-front Ag half of the length between each adja0.081 cm 353 cent front Ag grid 354 Front Ag finger width/height 50 μm/20 μm 355 n-rear Al 180, line array 30 μm 356 b-rear Al half of the length between each adja0.043 cm cent rear Al line 357 Front busbar (5 busbar width 0.08 cm 358 busbar) 359 Front Ag metal – 5.65% 360 fraction 361 Rear Al metal fraction – 3.25% 362 363 364 365 industrial batch of China Sunergy's Al2 O 3 PERC cell, tested in house under standard conditions 366 (i.e., the same I-V test criteria used as Fraunhofer ISE). 367 An example of a representative Al2O3 PERC cell (sample A) measured by illumination-Voc is shown 368 in Fig. 8, where the sample was tested before light-induced degradation (LID). 369 The series resistance (Rs) of the industrial Al2O3 PERC cell is shown in Table 1, calculated according 370 to Meier's method [4]. This calculation method is based on the measurement of Rs components in a 371 sub-cell (the measurement array), shown as key measurement in Table 1. The resistance in the dif372 ferent regions of the sub-cell array was measured by the grid resistance tester, while the specific 373 contact resistance was measured by the grid resistance tester based on the transmission line model 374 (TLM) method [5]. In addition, Table 2 provides the basic information of the design pattern of the 375 front Ag contact, which can support the calculation of Table 1. The detailed interpretation of the 376 calculation results can be found in Ref. [1]. 377 378
Please cite this article as: H. Huang, et al., Data of ALD Al2O3 rear surface passivation, Al2O3 PERC cell performance, and cell efficiency loss mechanisms of Al2O3 PERC cell, Data in Brief (2016), http: //dx.doi.org/10.1016/j.dib.2016.12.030i
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379 Acknowledgements 380 381 The research work is based on the China-Finland International R&D Cooperation Project “Improved 382 cost-efficiency in crystalline silicon solar cells through Atomic Layer Deposited Al2O3”, Project No. 383 40843 (Chinese Project No. S2013GR0622), 2013.05–2016.05. 384 385 386 Transparency document. Supporting material 387 388 Q3 Transparency data associated with this paper can be found in the online version at http://dx.doi. 389 org/10.1016/j.dib.2016.12.030. 390 391 392 References 393 394 [1] H. Huang, J. Lv, Y. Bao, R. Xuan, S. Sun, S. Sneck, S. Li, C. Modanese, H. Savin, A. Wang, J. Zhao, 20.8% industrial PERC solar cell: ALD Al2O3 rear surface passivation, efficiency loss mechanisms analysis and roadmap to 24%, Sol. Energy Mater. Sol. 395 Cells 161 (2017) 14–30. 396 [2] R.A. Sinton, A. Cuevas, Contactless determination of current-voltage characteristics and minority-carrier lifetimes in 397 semiconductors from quasi-steady-state photoconductance data, Appl. Phys. Lett. 69 (1996) 2510–2512. [3] 〈https://www.semilab.hu/products/si/faast-cocos-mc.https://www.semilab.hu/products/pvi/pv-2000〉, 2016. 398 [4] D. Meier, E. Good, Determining components of series resistance from measurements on a finished cell, in: Proceedings of 399 the 4th WCPEC, 2006, pp. 1315–1318. 400 [5] D.L. Meier, D.K. Schroder, Contact resistance: its measurement and relative importance to power loss in a solar cell, IEEE Trans. Electron Devices 31 (1984) 647–653.
Please cite this article as: H. Huang, et al., Data of ALD Al2O3 rear surface passivation, Al2O3 PERC cell performance, and cell efficiency loss mechanisms of Al2O3 PERC cell, Data in Brief (2016), http: //dx.doi.org/10.1016/j.dib.2016.12.030i
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Contents lists available at ScienceDirect
Data in Brief journal homepage: www.elsevier.com/locate/dib
Data Article
Data of ALD Al2O3 rear surface passivation, Al2O3 PERC cell performance, and cell efficiency loss mechanisms of Al2O3 PERC cell Haibing Huang a,b,n, Jun Lv a, Yameng Bao b, Rongwei Xuan a, Shenghua Sun a, Sami Sneck c, Shuo Li b, Chiara Modanese b, Hele Savin b, Aihua Wang a, Jianhua Zhao a a
China Sunergy, No.123. Focheng West Road, Jiangning Zone, Nanjing, Jiangsu 211100, China Aalto University, Department of Micro and Nanosciences, Tietotie 3, Espoo 02150, Finland c Beneq Oy, P.O. Box 262, Vantaa 01511 , Finland b
a r t i c l e i n f o
abstract
Article history: Received 21 November 2016 Received in revised form 13 December 2016 Accepted 15 December 2016
This data article is related to the recently published article ‘20.8% industrial PERC solar cell: ALD Al2O3 rear surface passivation, efficiency loss mechanisms analysis and roadmap to 24%’ (Huang et al., 2017) [1]. This paper is about passivated emitter and rear cell (PERC) structures and it describes the quality of the Al2O3 rear-surface passivation layer deposited by atomic layer deposition (ALD), in relation to the processing parameters (e.g. pre-clean treatment, deposition temperature, growth per cycle, and film thickness) and to the cell efficiency loss mechanisms. This dataset is made public in order to contribute to the limited available public data on industrial PERC cells, to be used by other researchers. & 2016 Published by Elsevier Inc. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
n
DOI of original article: http://dx.doi.org/10.1016/j.solmat.2016.11.018 Corresponding author at: China Sunergy, No.123. Focheng West Road, Jiangning Zone, Nanjing, Jiangsu 211100, China. E-mail address: [email protected] (H. Huang).
http://dx.doi.org/10.1016/j.dib.2016.12.030 2352-3409/& 2016 Published by Elsevier Inc. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
Please cite this article as: H. Huang, et al., Data of ALD Al2O3 rear surface passivation, Al2O3 PERC cell performance, and cell efficiency loss mechanisms of Al2O3 PERC cell, Data in Brief (2016), http: //dx.doi.org/10.1016/j.dib.2016.12.030i
H. Huang et al. / Data in Brief ∎ (∎∎∎∎) ∎∎∎–∎∎∎
2
55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108
Specifications Table Subject area More specific subject area Type of data How data was acquired
Data format Experimental factors
Experimental features
Data source location
Data accessibility
Physics Silicon solar cells, device simulations Figures, tables, graphs, spectra Effective minority carrier lifetime, implied Voc, pseudo I-V and illuminationVoc curves by Sinton WCT-120 Suns-Voc tester [2]; I-V curves and cell performances of the Si solar cell by HALM I-V tester or at Fraunhofer ISE; Thickness and refractive index of dielectric films by Suntech ellipsometer; Fixed negative charges (Qf) and interface defect density (Dit) by Semilab SDI PV2000 [3]; Cross-sectional EDS analysis with Vantage-100 EDS instrument from Thermo Electron Corporation; Silicon solar cell series resistance components calculated using Meier's method[4]; Resistance in the sub-cell array measured by grid resistance tester; Contact resistance measured by grid resistance tester based on the transmission line model [5]. Raw and analyzed The wafer samples for lifetime, film thickness, refractive index, Qf, and Dit were treated in NaOH solution to remove saw damage and cleaned in HCl and HF before the ALD Al2O3 process. PERC cells were processed from B-doped, Czochralski-grown, pseudo-square, 6″ wafers with 190 mm thickness. The processing flow is: saw damage removal (NaOH) with random-pyramid texturing, POCl3 diffusion (front n þ emitter, 90 Ω/□ sheet resistance), edge isolation with rear side polishing (HNO3–HF– H2SO4 solution), ALD Al2O3 and PECVD SiNx rear side passivation stacks, local patterning with laser ablation (532 nm, ps-laser), screen printing and cofiring for front (Ag/n þ –Si ohmic contact) and rear side metallization (Al local back surface field and local Al/p þ –Si Ohmic contact). For cell measurements, the completed solar cells were tested before lightinduced degradation after storage in a nitrogen gas cabinet. Cross-sectional SEM/EDS analysis on the local Al–Si rear contact areas was done on three cross sections along the (110) crystallographic orientation with an angle of 45° with respect to the local line contacts at the rear. The focus is on ozone (O3) and Al(CH3)3 trimethylaluminium (TMA) based thermal ALD process, implemented by Beneq's industrial P800 batch ALD tool. Temperature is 200 °C, Al2O3/SiNx thickness ratio is 10 nm/100 nm, deposition pressure is 150–500 Pa, rapid thermal processing (RTP) firing is at 760 °C peak temperature in compressed air for 2–3 s. The effective minority carrier lifetime and implied Voc measurements were carried out with the generalized mode, 5 1015 cm 3 injection level and optical constant of 0.7 for Si (100) surfaces and 0.85–0.95 for Al2O3/SiNx stack. ALD Al2O3 process pressure and post-ALD anneal temperature and time were monitored by the process tool. (1) China Sunergy, No.123. Focheng West Road, Jiangning Zone, Nanjing, Jiangsu, 211100, China (2) Aalto University, Department of Micro and Nanosciences, Tietotie 3, 02150 Espoo, Finland Data is within this article and in Ref. [1]
Please cite this article as: H. Huang, et al., Data of ALD Al2O3 rear surface passivation, Al2O3 PERC cell performance, and cell efficiency loss mechanisms of Al2O3 PERC cell, Data in Brief (2016), http: //dx.doi.org/10.1016/j.dib.2016.12.030i
H. Huang et al. / Data in Brief ∎ (∎∎∎∎) ∎∎∎–∎∎∎
Value of the data
The data on the quality of the atomic layer deposition (ALD) Al2O3 rear surface passivation and on
front Ag metallization pattern design provides a valuable dataset on the current industrial PERC structure and potentials, which can be used by researchers for the optimization of the current cell processes. The interplay between different parameters provides an overall description of the Al2O3 rear surface passivation process which leads to the optimal final passivation quality. The analysis on the loss mechanisms gives a relevant indication of the relative importance of different processing parameters via the calculation of the series resistance for the various components of the PERC cell. The data presented is collected from an extensive database from industrial PERC cells, and can thus be used by other researchers as a benchmark for industrial performances.
1. Data The dataset of this paper provides additional information to Ref. [1]. The rear surface passivation quality in relation to the ALD Al2O3 processing parameters is reported in Figs. 1–5, the PERC cell properties are reported in Figs. 6–8 and Table 1, and the metal contact design pattern and parameters are reported in Table 2.
2. Experimental design, materials and methods The procedure prior to the minority carrier lifetime measurements on the ALD Al2O3 rear surface passivation is described in detail in Fig. 1 in Ref. [1] and the most relevant aspects are reported here. All samples underwent saw damage removal and pre-ALD clean, followed by ALD Al2O3 deposition with varying parameters. Post-ALD anneal was performed on most of the samples, and then followed by plasma enhanced chemical vapor deposition (PECVD) of the SiNx capping layer. Afterwards, since lifetime cannot be measured after metallization, the samples were divided into two groups; one group directly underwent rapid thermal processing (RTP) firing, whereas a second group first underwent screen-printing of Al paste, then RTP firing followed by Al paste removal. All the samples were then measured under similar parameters. The interface defect density (Dit), the negative fixed charges (Q f) and open circuit voltage (Voc) as a function of the pre-ALD clean parameters are reported in Fig. 1. SC1 and SC2 pre-clean can achieve the best passivation quality (both regarding Dit and Voc). The pre-ALD clean does not affect the amount of Q f. Note that in the industrial PERC cell process, edge isolation and rear side polishing prior to the Al2O3 process normally terminate with HCl–HF clean sub-step.
Dit Qf
2.5x1011 2.0x1011
-2.0x1012
1.5x1011 1.0x10
Avg. Voc Best Voc
662
-1.5x1012 Voc (mV)
Dit at midgap(cm-2ev-1)
664
-1.0x1012
3.0x1011
Qf (cm-2)
109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162
3
660
-2.5x1012
658
-3.0x1012
656
11
No pre-clean
HCl-HF
HF-SC1-SC2-HF
Pre-ALD clean process
2-HF HCl-HF HF-SC1-SC Pre-ALD clean process
Fig. 1. Dit and Q f (a) and Voc (b) as a function of pre-ALD clean for Al2O3 passivation.
Please cite this article as: H. Huang, et al., Data of ALD Al2O3 rear surface passivation, Al2O3 PERC cell performance, and cell efficiency loss mechanisms of Al2O3 PERC cell, Data in Brief (2016), http: //dx.doi.org/10.1016/j.dib.2016.12.030i
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4
After Firing
After Al paste removal
700
20.6
660
600
400 300
656 20.2
ηcell (%)
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Voc (mV)
Effective minority lifetime(μs)
652
200
20.0
100 0
19.8
648 160
200
240
275
160
ALD Process Temperature (°C)
200
240
275
ALD Process Temperature (°C)
Fig. 2. Effective minority carrier lifetime (a) and cell performance (b) as a function of ALD temperature for Al2O3 passivation.
1.05
1.64 1.62
1.00
1.60 0.95 ALD growth rate Refractive index 0.90
160
200
240
Refractive index
ALD growth rate ( /cycle)
163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216
1.58 275
ALD process temperature (°C) Fig. 3. Growth rate (Å/cycle) and refractive index as a function of ALD process temperature.
The effect of the ALD process temperature for Al2O3 passivation on effective minority carrier lifetime and PERC cell performance (as Voc and cell efficiency (ηcell)) is reported in Fig. 2, while the effect on growth rate and refractive index (nk) of the dielectric layer is shown in Fig. 3. Our data show that the optimal temperature for passivation (in relation to both the effective lifetime and ηcell) is in the range of 200–240 °C, whereas the passivation level drops sharply at 275 °C. Note also that the process window between 160 and 240 °C is broad. In addition, the growth rate begins to decrease for temperatures above 200 °C. The refractive index is relatively low below 200 °C (nk ¼1.57), and it is stable (nk ¼1.63–1.65) between 200 and 400 °C. The optimal temperature for growth rate and refractive index is also around 200 °C. Fig. 4 shows the passivation quality as effective minority carrier lifetime, PERC cell performance (Voc and ηcell), Dit and Qf as a function of the Al2O3 film thickness. Effective minority lifetime and cell performance gradually increase with thickness increasing from 3.5 to 16 nm, where the optimal thickness is 10 nm. When the film thickness increases from 3.5 to 16 nm, cell performances and Dit gradually improve, while Qf is at the same level. Note that even a thin Al2O3 film of about 3.5 nm can work well on PERC cell (Voc E652 mV and ηcell E20.3%). SEM/energy dispersive X-ray spectroscopy (EDS) analysis on the effect of voids on the local back surface field (LBSF) rear local contact was performed and is shown in Fig. 5. Note that the spectra in the figure are from the Al-Si eutectic, the Al LBSF and the Si substrate, respectively. The detailed interpretation of the differences among the spectra is given in Ref. [1]. The thickness of the Al LBSF layer is 10 μm, thus revealing that the junction depth is deeper than 10 μm. Representative examples of industrial PERC cell performances are reported in Figs. 6,7. The certified current-voltage (I-V) curve and cell performance of one SiO 2 -PERC cell was measured at Please cite this article as: H. Huang, et al., Data of ALD Al2O3 rear surface passivation, Al2O3 PERC cell performance, and cell efficiency loss mechanisms of Al2O3 PERC cell, Data in Brief (2016), http: //dx.doi.org/10.1016/j.dib.2016.12.030i
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Avg. V
Best T
800
Avg. η
Best V
Best η
20.7
660 658
20.6
Voc (mV)
600
400
656 20.5 654 20.4
652
200
20.3
650 6 nm
11 nm
16 nm
3.5 nm
Al2O3 film thickness (nm)
11 nm
16 nm
Al2O3 film thickness (nm)
11
0 Dit
-1
Dit at midgap ( cm ev )
6x10
6 nm
-2
Qf 4x1011
-1x10
12
2x1011
-2x10
12
0
Qf(cm-2)
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ηcell (%)
Avg. T Effective minority lifetime (μs)
217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270
5
-3x1012 3.5 nm
6 nm
11 nm
16 nm
Al2O3 film thickness (nm) Fig. 4. Effective minority carrier lifetime (a), Voc and ηcell (b), Dit and Qf (c) as a function of Al2O3 film thickness for Al2O3 passivation.
Fig. 5. Cross-sectional EDS analysis of the Al-Si contact areas (Fig. 14-c and Table 4 in Ref. [1]). Here, point 1 (pt1): Al-Si alloy, point 2 (pt2): Al LBSF, and point 3 (pt3): Si substrate.
Fraunhofer ISE in July 2013 under standard test conditions (see Fig. 6). Note that the key process in this structure is rear surface passivation with thermal oxidation and dielectric opening with Merck's chemical paste. Fig. 7 shows a typical example of the cell efficiency of an average
Please cite this article as: H. Huang, et al., Data of ALD Al2O3 rear surface passivation, Al2O3 PERC cell performance, and cell efficiency loss mechanisms of Al2O3 PERC cell, Data in Brief (2016), http: //dx.doi.org/10.1016/j.dib.2016.12.030i
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Fig. 6. Cell performance and I-V curve of one SiO2-PERC cell example (before light induced degradation) tested by Fraunhofer ISE in July 2013 (under Standard Test Condition of global AM1.5, 1000 W m 2, 25 °C).
Ncell Avg. cell efficiency: 20.22%
21.0 20.5
Ncell (%)
20.0 19.5 19.0 18.5 18.0 0
250
500
750 1000 1250 1500 1750 2000
Cell No. Fig. 7. The scatter diagram of the industrial Al2O3 PERC cell performance ( 2000 PERC cells/batch, before light induced degradation).
Voltage (V)
Measured Suns-Voc
10.000 Illumination (Suns)
Pseudo Light IV curve without the effect of Rs 0.045 0.028 0.04 0.035 0.03 0.019 0.025 0.02 0.015 0.009 0.01 0.005 0 0.000 0.00 0.20 0.40 0.60 0.80
Power Density (W/cm2)
Current (A/cm2)
271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324
Double Diode Fit
1.000 0.100 0.010 0.001 0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
Open Circuit Voltage (Volts)
Fig. 8. Suns-Voc measurement of the PERC cell sample A (Table 5 in Ref. [1]): pseudo I-V curve (left) and illumination-Voc (right).
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325 Table 1 326 Q2 The calculation of series resistance of the industrial Al2O3 PERC cell using Meier's method [4]. 327 Description Key measurement Specific resisresistance Fraction 328 tance (Ω cm2) (mΩ) 329 Item Measured value 330 1. Front Ag busbar Resistance length 0.098 0.0073 0.0299 1.22% 331 of busbar 332 2. Rear AgAl busbar Similar to front estimated 0.0040 0.0165 0.67% 333 busbar 3. Front Ag grid Busbar-to-busbar 0.055 Ω 0.2197 0.9070 36.82% 334 resistance 335 0.009 Ω/□ 0.0419 0.1730 7.02% 4. Rear Al metallization Rsheet_metal 336 5. Front n þ emitter Rsheet_emitter 90 Ω/□ 0.1971 0.8137 33.03% 337 6. Rear Si substrate lateral Rsheet_Si substrate 121 Ω/□ 0.0746 0.3081 12.51% 338 spreading resistance 0.0161 0.0665 2.70% 7. Front Ag/n–Si contact TLM measurement Specific contact resis339 [5] tance: 3.1 mΩ cm2 340 8. Rear Al/p–Si contact TLM measurement Specific contact resis0.0030 0.0124 0.50% 341 [5] tance, estimated 342 9. p–Si substrate Resistivity, thick2 Ω cm, 165 μm 0.0330 0.1362 5.53% ness of wafer 343 – – 0.5967 2.4635 100% Rs-Total 344 345 346 347 348 Table 2 The basic information of the design pattern of the front Ag contact of the Al2O3 industrial PERC cell in this data article. 349 350 Key parameters Description Value 351 352 n-front Ag the number of front grid 96 b-front Ag half of the length between each adja0.081 cm 353 cent front Ag grid 354 Front Ag finger width/height 50 μm/20 μm 355 n-rear Al 180, line array 30 μm 356 b-rear Al half of the length between each adja0.043 cm cent rear Al line 357 Front busbar (5 busbar width 0.08 cm 358 busbar) 359 Front Ag metal – 5.65% 360 fraction 361 Rear Al metal fraction – 3.25% 362 363 364 365 industrial batch of China Sunergy's Al2 O 3 PERC cell, tested in house under standard conditions 366 (i.e., the same I-V test criteria used as Fraunhofer ISE). 367 An example of a representative Al2O3 PERC cell (sample A) measured by illumination-Voc is shown 368 in Fig. 8, where the sample was tested before light-induced degradation (LID). 369 The series resistance (Rs) of the industrial Al2O3 PERC cell is shown in Table 1, calculated according 370 to Meier's method [4]. This calculation method is based on the measurement of Rs components in a 371 sub-cell (the measurement array), shown as key measurement in Table 1. The resistance in the dif372 ferent regions of the sub-cell array was measured by the grid resistance tester, while the specific 373 contact resistance was measured by the grid resistance tester based on the transmission line model 374 (TLM) method [5]. In addition, Table 2 provides the basic information of the design pattern of the 375 front Ag contact, which can support the calculation of Table 1. The detailed interpretation of the 376 calculation results can be found in Ref. [1]. 377 378
Please cite this article as: H. Huang, et al., Data of ALD Al2O3 rear surface passivation, Al2O3 PERC cell performance, and cell efficiency loss mechanisms of Al2O3 PERC cell, Data in Brief (2016), http: //dx.doi.org/10.1016/j.dib.2016.12.030i
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379 Acknowledgements 380 381 The research work is based on the China-Finland International R&D Cooperation Project “Improved 382 cost-efficiency in crystalline silicon solar cells through Atomic Layer Deposited Al2O3”, Project No. 383 40843 (Chinese Project No. S2013GR0622), 2013.05–2016.05. 384 385 386 Transparency document. Supporting material 387 388 Q3 Transparency data associated with this paper can be found in the online version at http://dx.doi. 389 org/10.1016/j.dib.2016.12.030. 390 391 392 References 393 394 [1] H. Huang, J. Lv, Y. Bao, R. Xuan, S. Sun, S. Sneck, S. Li, C. Modanese, H. Savin, A. Wang, J. Zhao, 20.8% industrial PERC solar cell: ALD Al2O3 rear surface passivation, efficiency loss mechanisms analysis and roadmap to 24%, Sol. Energy Mater. Sol. 395 Cells 161 (2017) 14–30. 396 [2] R.A. Sinton, A. Cuevas, Contactless determination of current-voltage characteristics and minority-carrier lifetimes in 397 semiconductors from quasi-steady-state photoconductance data, Appl. Phys. Lett. 69 (1996) 2510–2512. [3] 〈https://www.semilab.hu/products/si/faast-cocos-mc.https://www.semilab.hu/products/pvi/pv-2000〉, 2016. 398 [4] D. Meier, E. Good, Determining components of series resistance from measurements on a finished cell, in: Proceedings of 399 the 4th WCPEC, 2006, pp. 1315–1318. 400 [5] D.L. Meier, D.K. Schroder, Contact resistance: its measurement and relative importance to power loss in a solar cell, IEEE Trans. Electron Devices 31 (1984) 647–653.
Please cite this article as: H. Huang, et al., Data of ALD Al2O3 rear surface passivation, Al2O3 PERC cell performance, and cell efficiency loss mechanisms of Al2O3 PERC cell, Data in Brief (2016), http: //dx.doi.org/10.1016/j.dib.2016.12.030i