&gt;16% thin‐film epitaxial silicon solar cells on 70‐cm<sup>2</sup> area with 30‐µm active layer, porous silicon back reflector, and Cu‐based top‐contact metallization

Kuzma-Filipek, I.; Dross, Frédéric; Baert, Kasper; Hernández, José Luis; Singh, Sukhvinder; Nieuwenhuysen, Kris Van; Poortmans, Jozef

doi:10.1002/pip.1146

Cited by 22 publications

(22 citation statements)

References 10 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The efficiency of our HJS solar cells was much lower than that of solar cells with kerfless Si as a substrate. 6,7,9,10 To determine why the efficiency of the HJS solar cell was low, we investigated the microstructure and chemically analyzed the exfoliated Si(111) substrate. Figures 4a and 4b respectively show an SEM image and the EDX analysis of the metal-removed side of the exfoliated Si(111) substrate.…”

Section: Resultsmentioning

confidence: 99%

“…6 Petermann et al used a 43-μm-thick and freestanding epitaxial Si film by using the layer transfer technique to obtain a 19% efficient Si solar cell.…”

mentioning

confidence: 99%

“…6 Petermann et al used a 43-μm-thick and freestanding epitaxial Si film by using the layer transfer technique to obtain a 19% efficient Si solar cell. 7 High-efficiency solar cells can be fabricated using these thin epitaxial Si substrates; however, the high-temperature fabrication process (>1000…”

mentioning

confidence: 99%

See 2 more Smart Citations

Fabricating 43-μm-Thick and 12% Efficient Heterojunction Silicon Solar Cells by Using Kerfless Si(111) Substrates

Chen

Wang

et al. 2015

ECS J. Solid State Sci. Technol.

View full text Add to dashboard Cite

A 43-μm-thick Si(111) substrate was obtained using the stress-induced lift-off method with a screen-printed metal paste layer as the stress-generation layer. The reflection of the metal-removed side of the Si(111) substrate was lower than that of the exfoliated side because of high surface roughness resulting from the reaction between the metal paste and the silicon substrate at 700 • C. After aggressive etching with an alkaline solution for the peeled silicon substrate, the efficiency of the heterojunction silicon solar cell was improved from 0.87% to 12%. For decades, silicon (Si)-based solar cells have been the conventionally used products in the photovoltaic (PV) industry. The Si solar cell module price is lower than 0.75 USD/W, which could be mainly attributed to the extensive research on and development of these cells and support from local governments.1 Although the price of poly-Si decreased markedly from 450 USD/kg in 2008 to 20 USD/kg in 2015, the price of poly-Si accounts for more than 50% of the cost of a Si solar cell.2 Thus, reducing the use of Si is the most effective method for reducing the cost of a Si solar cell. Therefore, the thickness of a Si substrate will be reduced from 200 μm in 2010 to 120 μm in 2020.2 In addition, reducing the thickness can further increase the cell efficiency, which is generally achieved by enhancing the open circuit voltage (Voc).3,4 Recently, a 98-μm-thick and 24.7% efficient heterojunction Si (HJS) solar cell, with a Voc of 750 mV, was developed by Panasonic. 5Using a thin Si substrate obtained by applying a kerfless process, which can potentially reduce the cost of solar cells, has become a major topic recently.6-11 Kuzma-Filipek et al. used a 30-μm-thick epitaxial Si film grown on a highly doped P + -Si substrate with a porous multilayer structure to obtain a 16.2% efficient Si solar cell. 6 Petermann et al. used a 43-μm-thick and freestanding epitaxial Si film by using the layer transfer technique to obtain a 19% efficient Si solar cell.7 High-efficiency solar cells can be fabricated using these thin epitaxial Si substrates; however, the high-temperature fabrication process (>1000• C) and expensive epitaxy system increase the cost. The stress-induced lift-off method, which is based on the thermal expansion difference between a deposited metal film and a Si substrate, could be an alternative because it entails a simple, low-temperature (<900• C) process for obtaining a thin Si substrate. 8,12,13 Dross et al. compared the differences between Si(111) and Si(100) substrates after exfoliation and obtained a 50-μm-thick and 10% efficient Si solar cell.9 Saha et al. further alleviated the difficulty of handling thin Si substrates and obtained a 25-μm-thick and 14.9% efficient Si solar cell. 10 We recently reported the thermal stress-induced pattern transfer technique, which is a combination of the thin-film deposition process and the layer transfer technique, and obtained a 3-μm-thick Si film with a textured surface. The short-circuit current of the HJS solar cell fabr...

show abstract

Section: Resultsmentioning

confidence: 99%

“…6 Petermann et al used a 43-μm-thick and freestanding epitaxial Si film by using the layer transfer technique to obtain a 19% efficient Si solar cell.…”

mentioning

confidence: 99%

See 1 more Smart Citation

Fabricating 43-μm-Thick and 12% Efficient Heterojunction Silicon Solar Cells by Using Kerfless Si(111) Substrates

Chen

Wang

et al. 2015

ECS J. Solid State Sci. Technol.

View full text Add to dashboard Cite

show abstract

“…Moreover, it was also observed that in some circumstances, the open‐circuit voltage ( V OC ) of epicells with porous silicon is about 20 mV lower than that of epicells without porous silicon. However, this dependence of V OC is not systematic . The second adverse effect of the porous silicon layer is because it presents a large surface area for recombination at the interface between the active layer and the substrate.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of the influence of an embedded porous silicon layer on the bulk lifetime of epitaxial layers and the interface recombination at the epitaxial layer/porous silicon interface

Radhakrishnan

Dross

Debucquoy

et al. 2013

Progress in Photovoltaics

Self Cite

View full text Add to dashboard Cite

Porous silicon plays an important role in the concept of wafer-equivalent epitaxial thin-film solar cells. Although porous silicon is beneficial in terms of long-wavelength optical confinement and gettering of metals, it could adversely affect the quality of the epitaxial silicon layer grown on top of it by introducing additional crystal defects such as stacking faults and dislocations. Furthermore, the epitaxial layer/porous silicon interface is highly recombinative because it has a large internal surface area that is not accessible for passivation. In this work, photoluminescence is used to extract the bulk lifetime of boron-doped (1016/cm3) epitaxial layers grown on reorganised porous silicon as well as on pristine mono-crystalline, Czochralski, p+ silicon. Surprisingly, the bulk lifetime of epitaxial layers on top of reorganised porous silicon is found to be higher (~100-115s) than that of layers on top of bare p+ substrate (32-50s). It is believed that proper surfa ce closure prior to epitaxial growth and metal gettering effects of porous silicon play a role in ensuring a higher lifetime. Furthermore, the epitaxial layer/porous silicon interface was found to be ~250 times more recombinative than an epitaxial layer/p+ substrate interface (S103cm/s). However, the inclusion of an epitaxially grown back surface field on top of the porous silicon effectively shields minority carriers from this highly recombinative interface

show abstract

“…Epicells fabricated on mono‐crystalline p + Czochralski (Cz) silicon wafers without any light trapping schemes have resulted in 16.5% efficiency for a 40 µm‐thick epilayer 8. Similarly, epicells with a porous silicon reflector fabricated on p + Cz silicon wafers have resulted in 16.9% efficiency (25 µm‐thick epilayer) on 4 cm 2 area 9 and 16.2% efficiency (30 µm‐thick epilayer) on 70 cm 2 area 10.…”

Section: Introductionmentioning

confidence: 99%

Gettering of transition metals by porous silicon in epitaxial silicon solar cells

Radhakrishnan

Ahn

Hoeymissen

et al. 2012

Physica Status Solidi (a)

Self Cite

View full text Add to dashboard Cite

Epitaxial silicon solar cells (“epicells”) are based on an epitaxial active layer (“epilayer”) grown on top of a low‐cost, inactive p+ silicon substrate. A key challenge is to mitigate transition metal out‐diffusion from the low‐purity substrate into the active layer. An embedded porous silicon (PSi) layer can be used to getter metals within the substrate. This was studied theoretically using density functional theory where large binding energies (∼1.9–2.2 eV) for metal segregation to PSi void surface were calculated for Fe and Cu. Incorporating this in a diffusion model yielded large gettering coefficients of ∼104 even at 1000 °C. To verify this experimentally, a test structure consisting of a 2‐µm thick epilayer grown on top of an 8.5 × 8.5 cm2 area of re‐organized PSi etched into the middle of an 8″ Cz, p+ wafer was used. These wafers were surface‐contaminated with metals (Fe, Ni, Cu) to ∼1014–1015 cm−2 and annealed at high temperatures (950–1000 °C) for up to 15 min. This allowed the metals to distribute throughout the wafer and getter to preferential sites. Direct total reflection X‐ray fluorescence mapping of Cu on the front side showed that the embedded PSi reduced the amount of Cu reaching the top surface by ∼103 times, compared to the areas without PSi. Moreover, SIMS depth profiling revealed large metal concentrations (1018–1019 cm−3) in the depth associated with PSi, while the metal concentrations were below detection limits in the surrounding area, suggesting a gettering coefficient of ∼103–104. A slow cooling rate and smaller pore radii were also found to be beneficial for gettering.

show abstract

>16% thin‐film epitaxial silicon solar cells on 70‐cm² area with 30‐µm active layer, porous silicon back reflector, and Cu‐based top‐contact metallization

Cited by 22 publications

References 10 publications

Fabricating 43-μm-Thick and 12% Efficient Heterojunction Silicon Solar Cells by Using Kerfless Si(111) Substrates

Fabricating 43-μm-Thick and 12% Efficient Heterojunction Silicon Solar Cells by Using Kerfless Si(111) Substrates

Evaluation of the influence of an embedded porous silicon layer on the bulk lifetime of epitaxial layers and the interface recombination at the epitaxial layer/porous silicon interface

Gettering of transition metals by porous silicon in epitaxial silicon solar cells

Contact Info

Product

Resources

About

>16% thin‐film epitaxial silicon solar cells on 70‐cm2 area with 30‐µm active layer, porous silicon back reflector, and Cu‐based top‐contact metallization

Cited by 22 publications

References 10 publications

Fabricating 43-μm-Thick and 12% Efficient Heterojunction Silicon Solar Cells by Using Kerfless Si(111) Substrates

Fabricating 43-μm-Thick and 12% Efficient Heterojunction Silicon Solar Cells by Using Kerfless Si(111) Substrates

Evaluation of the influence of an embedded porous silicon layer on the bulk lifetime of epitaxial layers and the interface recombination at the epitaxial layer/porous silicon interface

Gettering of transition metals by porous silicon in epitaxial silicon solar cells

Contact Info

Product

Resources

About

>16% thin‐film epitaxial silicon solar cells on 70‐cm² area with 30‐µm active layer, porous silicon back reflector, and Cu‐based top‐contact metallization