Highly passivating and blister-free hole selective poly-silicon based contact for large area crystalline silicon solar cells

Morisset, Audrey; Cabal, R.; Grange, Bernadette; Marchat, Clément; Alvarez, José; Gueunier‐Farret, Marie‐Estelle; Dubois, Sébastien; Kleider, Jean‐Paul

doi:10.1016/j.solmat.2019.109912

Cited by 41 publications

(39 citation statements)

References 46 publications

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“…The hydrogen effusion is indeed an isotropic process; therefore, a portion of hydrogen may be trapped at the interface between the growing www.nature.com/scientificreports www.nature.com/scientificreports/ film and substrate, resulting in blisters in the as-deposited state. It should also be pointed out that the fine-tuning of PECVD parameters, such as the relative gas flow ratio, can suppress blistering 26 . However, in this study, we tested the effect of substrate temperature at a constant gas flow ratio.…”

Section: Resultsmentioning

confidence: 99%

“…Therefore, the deposition of a silicon thin film with no hydrogen content should be key to prevent blister formation during TOPCon formation. As mentioned earlier, a low hydrogen content can be achieved by controlling PECVD parameters such as the relative gas flow ratio, resulting in the suppression of blisters 26 . For PECVD samples, the intensities of both the wagging-mode band and stretching-mode band gradually decrease with increasing substrate temperature.…”

Section: Resultsmentioning

confidence: 99%

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Formation and suppression of hydrogen blisters in tunnelling oxide passivating contact for crystalline silicon solar cells

Choi

Kwon

Min

et al. 2020

Sci Rep

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the formation of hydrogen blisters in the fabrication of tunnelling oxide passivating contact (topcon) solar cells critically degrades passivation. in this study, we investigated the formation mechanism of blisters during the fabrication of topcons for crystalline silicon solar cells and the suppression of such blisters. We tested the effects of annealing temperature and duration, surface roughness, and deposition temperature on the blister formation, which was suppressed in two ways. first, topcon fabrication on a rough surface enhanced adhesion force, resulting in reduced blister formation after thermal annealing. Second, deposition or annealing at higher temperatures resulted in the reduction of hydrogen in the film. A sample fabricated through low-pressure chemical vapor deposition at 580 °C was free from silicon-hydrogen bonds and blisters after the TOPCon structure was annealed. Remarkably, samples after plasma-enhanced chemical vapor deposition at 300, 370, and 450 °C were already blistered in the as-deposited state, despite low hydrogen contents. Analysis of the hydrogen incorporation, microstructure, and deposition mechanism indicate that in plasma-enhanced chemical vapor deposition (pecVD) deposition, although the increase of substrate temperature reduces the hydrogen content, it risks the increase of porosity and molecular-hydrogen trapping, resulting in even more severe blistering.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Formation and suppression of hydrogen blisters in tunnelling oxide passivating contact for crystalline silicon solar cells

Choi

Kwon

Min

et al. 2020

Sci Rep

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“…In standard passivating contact fabrication, a hydrogenated amorphous silicon (a-Si:H) layer is deposited, and then annealed for a long time at high temperature (usually 850°C for 30 min or more [5,[8][9][10]). This can lead to the formation of blisters.…”

Section: Pecvd Processmentioning

confidence: 99%

“…A single firing step, however, leads to even higher stress, resulting in an easier formation of blisters. One way to tackle this issue was to dilute SiH 4 into H 2 [10,11]. We deposited 1-2 nm of PECVD SiO x (30 s deposition), and subsequently deposited the boron doped silicon layer on top of it.…”

Section: Pecvd Processmentioning

confidence: 99%

Impact of PECVD μc-Si:H deposition on tunnel oxide for passivating contacts

et al. 2020

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Passivating contacts are becoming a mainstream option in current photovoltaic industry due to their ability to provide an outstanding surface passivation along with a good conductivity for carrier collection. However, their integration usually requires long annealing steps which are not desirable in industry. In this work we study PECVD as a way to carry out all deposition steps: silicon oxide (SiOx), doped polycrystalline silicon (poly-Si) and silicon nitride (SiNx:H), followed by a single firing step. Blistering of the poly-Si layer has been avoided by depositing (p+) microcrystalline silicon (μc-Si:H). We report on the impact of this deposition step on the SiOx layer deposited by PECVD, and on the passivation properties by comparing PECVD and wet-chemical oxide in this hole-selective passivating contact stack. We have reached iVoc > 690 mV on p-type FZ wafers for wet-chemical SiOx\(p+) μc-Si\SiNx:H with no annealing step.

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“…The full detail of the fabrication can be found elsewhere. 34 C-AFM technique was first applied on structures with highly doped poly-Si layers obtained after an annealing at 800°C, and specifically the measurements were realized after poly-Si surface deoxidation using a diluted HF treatment.…”

Section: C-afm and Kpfm Applied On Poly-si/siox/c-si Structuresmentioning

confidence: 99%

Electrical scanning probe microscopy approaches to investigate solar cell junctions and devices

Alvarez

Marchat

Morisset

et al. 2020

Quantum Sensing and Nano Electronics and Photonics XVII

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C-AFM and KPFM techniques have been applied to investigate advanced junctions that are currently involved in highly efficient silicon solar cells. Our first study focuses on silicon heterojunctions and notably hydrogenated amorphous silicon (a-Si:H)/crystalline silicon (c-Si) P/n or N/p heterostructures which band bending at the interface forms a 2D channel. This conductive channel was indeed evidenced for the first time by cross-sectional investigations by C-AFM confirming the analysis of macroscopic planar conductance measurements. A second example of nanoscale characterization concerns the passivating selective contacts consisting in a thin silicon oxide (SiOx) layer between the c-Si and a highly doped polysilicon (poly-Si) layer. The electrical carrier transport is here not limited by the oxide layer and it is assumed that tunnelling through the oxide and/or the presence of pinholes are the main competitive mechanisms. For this specific heterostructure KPFM reveals local surface potential drops of 15-30 mV, which do not exist on samples without SiOx. These potential drops suggest the presence of pinholes that are formed during the poly-Si annealing process performed in the range of 700-900 °C. Finally, in a third study, we concentrate on p-in radial junction (RJ) silicon nanowire (SiNW) devices that are investigated under illumination by KPFM, in the so-called surface photovoltage (SPV) technique. This work focuses on the possibility of extracting the open-circuit voltage (VOC) on single isolated SiNW RJ by local SPV measurements using different AFM tip shapes and illumination directions in order to minimize shadowing effects.

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Highly passivating and blister-free hole selective poly-silicon based contact for large area crystalline silicon solar cells

Cited by 41 publications

References 46 publications

Formation and suppression of hydrogen blisters in tunnelling oxide passivating contact for crystalline silicon solar cells

Formation and suppression of hydrogen blisters in tunnelling oxide passivating contact for crystalline silicon solar cells

Impact of PECVD μc-Si:H deposition on tunnel oxide for passivating contacts

Electrical scanning probe microscopy approaches to investigate solar cell junctions and devices

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