Void formation in screen-printed local aluminum contacts modeled by surface energy minimization

Kranz, Christopher; Baumann, Ulrike; Wolpensinger, Bettina; Lottspeich, Friedrich; Müller, M.; Palinginis, Phedon; Brendel, Rolf; Dullweber, Thorsten

doi:10.1016/j.solmat.2016.06.039

Cited by 19 publications

(8 citation statements)

References 16 publications

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“…The relatively deeper local Al‐BSF of the PERC+ is dependent on the narrower contact width and lower peak firing temperature as shown in Figure S2 (Supporting Information), which leads to higher silicon concentrations in the Al finger and a reduced number of voids, and lowers the local Al‐BSF recombination current density J 0,BSF from 500 to 350 fA/cm 2. To determine J 0,BSF as extracted by the quasi‐steady‐state photoconductance decay method, we use a different fraction of the local BSF area method . The SE improves the η of the PERC and PERC+ solar cells up to 21.6% and 21.7%, and the V OC to 672 and 679 mV, respectively.…”

Section: Resultsmentioning

confidence: 99%

Efficiency enhancement of bifacial PERC solar cells with laser‐doped selective emitter and double‐screen‐printed Al grid

Zhang

Zheng

et al. 2018

Progress in Photovoltaics

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We report that the application of a laser‐doped selective emitter (SE) can improve the trade‐off between the recombination in the emitter and the Ag‐Si specific contact resistance and that a double‐screen‐printed rear aluminum grid can decrease the series resistance in the industrial bifacial passivated emitter and rear cell (PERC). Our results reveal that a front‐side efficiency of 21.9% can be achieved in the PERC (SE)+ solar cell by using low surface‐recombination Al2O3/SiNx films as passivation layers, low‐recombination emitter, and low resistive Ag‐Si contact with an optimized sheet resistance of the lightly doped area of SE with 125Ω/sq and sheet resistance of the highly doped area of SE with 70 Ω/sq. The highest front‐side efficiency of 22.0%, with open‐circuit voltage of 680 mV, short‐circuit current density of 40.1 mA/cm2, and fill factors of 80.8%, is obtained by using double‐screen‐printed rear Al grid process, which is 0.1% higher than the best PERC (SE)+ solar cell. The rear‐side double‐layer antireflection coating consists of 50 nm SiNx:H (n = 2.1) and 10 nm SiNx:H (n = 2.37), which enables a large bifacial gain with the output power density PMPP of 25.5 mW/cm2 in the PERC (SE)+ solar cell by using double‐screen‐printed rear Al grid process when rear‐side illumination intensity Erear = 0.25 suns.

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Section: Resultsmentioning

confidence: 99%

Efficiency enhancement of bifacial PERC solar cells with laser‐doped selective emitter and double‐screen‐printed Al grid

Zhang

Zheng

et al. 2018

Progress in Photovoltaics

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“…Further analysis reveals that voids in particular occur for Al contacts where the Al-Si eutectic extends more than 20 µm deep into the Si wafer. 23) To explain this finding, we proposed an analytical model that calculates the surface energies of the liquid Al-Si melt, the Si wafer surface and the screen-printed Al particle surface. 23) According to this model, voids form for deep contacts since then during furnace firing a sufficient amount of Al-Si melt is available in order to wet the large surface area of Al particles rather than the small Si wafer surface area.…”

Section: Industrial Perc+ Solar Cellsmentioning

confidence: 99%

Present status and future perspectives of bifacial PERC+ solar cells and modules

Dullweber

Schulte‐Huxel

Blankemeyer

et al. 2018

Jpn. J. Appl. Phys.

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This paper reviews the main research results related to PERC+ silicon solar cells. Compared to today's industry typical passivated emitter and rear cell (PERC) silicon solar cells with full-area rear aluminum layer, PERC+ solar cells apply an aluminum finger grid on the rear side and hence are able to absorb diffuse light from the rear side in addition to the direct sunlight which is absorbed from the front side. This bifaciality increases the energy yield of silicon solar modules by up to 25%. Since its first publication in 2015, the PERC+ cell concept has been rapidly adopted by several solar cell manufacturers due to the very similar process technology of bifacial PERC+ cells and main stream monofacial PERC cells. We summarize technological challenges, published PERC+ conversion efficiencies and PERC+ module technologies. First energy yield data of PERC+ field installations demonstrate the high energy yield potential of PERC+ solar cells.

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“…SEMDCI has now been used widely to characterize industrial Si wafers with p‐type (boron) diffused emitters [ 18–22 ] and aluminum localized back surface contacts (LBSF). [ 23–33 ] However, reports of SEMDCI imaging of phosphorus emitters are less common, including homogeneous diffused emitters, [ 34–36 ] and localized selective emitters. [ 20,37 ] A more recent PV application of SEMDCI imaging has been characterizing nanotextured BSi.…”

Section: Introductionmentioning

confidence: 99%

“…SEMDCI has now been used widely to characterize industrial Si wafers with p-type (boron) diffused emitters [18][19][20][21][22] and aluminum localized back surface contacts (LBSF). [23][24][25][26][27][28][29][30][31][32][33] However, reports of SEMDCI Phosphorous dopant diffusion profiles feature in many silicon semiconductor devices, including the vast majority of silicon solar cells. Accurate spatially resolved dopant profiling is crucial for understanding the performance of these diffused regions, however, it is very challenging to obtain such profiles in non-planar samples.…”

mentioning

confidence: 99%

Scanning Electron Microscopy Dopant Contrast Imaging of Phosphorus‐Diffused Silicon

Zhang

Scardera

Wang

et al. 2022

Adv Materials Technologies

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Phosphorous dopant diffusion profiles feature in many silicon semiconductor devices, including the vast majority of silicon solar cells. Accurate spatially resolved dopant profiling is crucial for understanding the performance of these diffused regions, however, it is very challenging to obtain such profiles in non‐planar samples. Scanning electron microscopy for dopant contrast imaging (SEMDCI), where the secondary electron (SE) image contrast is used to determine the dopant level of a semiconductor sample, is an ideal candidate for Si dopant profiling, especially for silicon samples with surface nanotexturing or black silicon (BSi) technology. However, in previous SEMDCI studies, the dopant concentration of heavily doped n‐type layers in silicon samples have shown a poor correlation with the SE signal contrast. In this work, 1) good contrast for n‐type diffused silicon without contrast‐enhancing techniques; 2) a new contrast definition to account for imaging non‐uniformities; 3) clear correlations between SE contrast and sample work function for phosphorus‐diffused planar silicon specimens across a wide range of emitter profiles; 4) implementation of an empirical baseline correction to normalize scanning electron microscopy image condition variations, are presented. This SEMDCI method is subsequently used for the first time to obtain 2D electron concentration maps for both planar and BSi samples.

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Void formation in screen-printed local aluminum contacts modeled by surface energy minimization

Cited by 19 publications

References 16 publications

Efficiency enhancement of bifacial PERC solar cells with laser‐doped selective emitter and double‐screen‐printed Al grid

Efficiency enhancement of bifacial PERC solar cells with laser‐doped selective emitter and double‐screen‐printed Al grid

Present status and future perspectives of bifacial PERC+ solar cells and modules

Scanning Electron Microscopy Dopant Contrast Imaging of Phosphorus‐Diffused Silicon

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