IBC c-Si solar cells based on ion-implanted poly-silicon passivating contacts

Yang, Guangtao; Ingenito, Andrea; Isabella, Olindo; Zeman, Miro

doi:10.1016/j.solmat.2016.05.041

Cited by 82 publications

(64 citation statements)

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“…Considering these achievements, integrating passivating contacts in a back-contacted architecture is the obvious c-Si single-junction solar-cell design towards highest conversion efficiencies. Such an approach has increasingly been researched in both academia and industry over the past decade [14][15][16][17][18][19][20][21] , resulting in the past few years in several record devices with efficiencies ≥25% (refs 22-26). Technologically, it is of note that all these outstanding results have been reached with passivating contacts that are either silicon-oxide-based 22 or fabricated by low-temperature depositions of hydrogenated silicon thin films [24][25][26] , distinctive of the so-called silicon heterojunction (SHJ) technology (ref.…”

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confidence: 99%

Simple processing of back-contacted silicon heterojunction solar cells using selective-area crystalline growth

et al. 2017

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For crystalline-silicon solar cells, voltages close to the theoretical limit are nowadays readily achievable when using passivating contacts. Conversely, maximal current generation requires the integration of the electron and hole contacts at the back of the solar cell to liberate its front from any shadowing loss. Recently, the world-record e ciency for crystalline-silicon singlejunction solar cells was achieved by merging these two approaches in a single device; however, the complexity of fabricating this class of devices raises concerns about their commercial potential. Here we show a contacting method that substantially simplifies the architecture and fabrication of back-contacted silicon solar cells. We exploit the surface-dependent growth of silicon thin films, deposited by plasma processes, to eliminate the patterning of one of the doped carrier-collecting layers. Then, using only one alignment step for electrode definition, we fabricate a proof-of-concept 9-cm 2 tunnel-interdigitated backcontact solar cell with a certified conversion e ciency >22.5%. I n recent decades, the market of photovoltaics has been consistently growing and the yearly installed photovoltaic capacity has increased from 328 MW peak in 2001 to 50 GW peak in 2015. This resulted in 2016 in a cumulative capacity of 235 GW peak (ref. 1), largely based on crystalline-silicon (c-Si) solar-cell technologies 2 , and contributing to about 1.3% of the global electricity production 3 . To further increase this number, the cost-competitiveness of photovoltaics must surpass that of classic, non-renewable energy sources, and one route towards this goal is to raise the conversion efficiency of industrial c-Si solar cells 4,5 .High power conversion efficiencies require maximizing the solar-cell electrical parameters: open-circuit voltage (V oc ), fillfactor (FF) and short-circuit current density (J sc ). For the V oc and FF, this is possible by using passivating contacts, employing silicon oxide or hydrogenated amorphous silicon (a-Si:H) thin films to minimize charge carrier recombination at the electrical contacts to the c-Si wafer, with demonstrated record efficiencies for two-sidecontacted solar cells of 25.1% (refs 6,7). Maximum J sc values can be achieved using a back-contacted architecture, eliminating front metal electrode shadowing and minimizing optical reflection and absorption losses at the front. Small-sized back-contacted solar cells, based on diffused silicon homo-junctions, were realized at several research institutes (refs 8-11), showing a best conversion efficiency up to 24.4% (ref. 12). Industrially, the back-contacted architecture was pioneered by Sunpower, recently reporting on large-area devices with very high J sc values and efficiencies surpassing 25% (ref. 13). Considering these achievements, integrating passivating contacts in a back-contacted architecture is the obvious c-Si single-junction solar-cell design towards highest conversion efficiencies. Such an approach has increasingly been researched in both academia and indust...

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Simple processing of back-contacted silicon heterojunction solar cells using selective-area crystalline growth

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“…From this approach, m e , m h , E B e and E B h are the parameters inherent to the dielectric material used as tunneling oxide (uniform SiO 2 ), but r ox is related to device process. [22], [53]. The absorber bulk is c-Si n-type.…”

Section: B Tunnelingmentioning

confidence: 99%

“…2 shows the two-dimensional (2-D) cross section of the poly-Si IBC solar cell symmetry element used to perform optoelectrical simulations. The model has been developed based on a reference IBC solar cell featuring a 280-μm thick, 5-Ω·cm resistivity FZ c-Si n-type wafer and a 650-μm-wide pitch [22]. Consistent with processed device, the front interface is texturized by random pyramids and covered by a thermal SiO 2 and a SiNx deposited by plasma enhanced chemical vapor deposition (PECVD) as anti-reflective coating (ARC).…”

Section: B Tunnelingmentioning

confidence: 99%

“…In the first case, pinholes are formed by increasing the annealing temperature above 1000°C in oxide layers above 2 nm [20]. In the second case, the transport of carriers is described by tunneling through a potential energy barrier built by an oxide layer around 1.5 nm thick [22], [30]- [33], implying process temperatures lower than 950°C. It is worth noting that several studies within state-of-the-art complementary metal oxide semiconductor (CMOS) devices [34]- [40] confirm that leakage currents though thin dielectrics are based on tunneling.…”

Section: Introductionmentioning

confidence: 99%

“…Here, based on an advanced two-dimensional opto-electrical model, we investigate the mechanisms leading to main losses in poly-Si-based IBC reference solar cell [22]. After, we identify the main competitive physical mechanisms that are related to process fabrication and enable high fill factor (FF) and V oc .…”

Section: Introductionmentioning

confidence: 99%

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Numerical Simulations of IBC Solar Cells Based on Poly-Si Carrier-Selective Passivating Contacts

Procel

Yang

Isabella

et al. 2019

IEEE J. Photovoltaics

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This paper presents an analysis of physical mechanisms related to operation and optimization of interdigitated back contact (IBC) poly-silicon-based devices. Concepts of carrier selectivity and tunneling are used to identify the parameters that impact on the fill factor. Then, based on technology computer-aided design (TCAD) numerical simulations, we describe the device performance in terms of transport and passivation. A validation of the model is performed by matching measured and simulated R, T, and external quantum efficiency spectra and electrical parameters. As result of such process, the opto-electrical losses of the reference device are identified. Then, we execute a study of the impact of process parameters on the performance of the IBC device under analysis. Assuming a uniform SiO 2 layer, simulation results reveal that both n-type and p-type poly-Si contacts can be theoretically perfect (i.e., approx. lossless), if assuming no interface recombination but considering tunneling of both carrier types. In other words, there exists an optimum oxide thickness (1 nm) for which majority carriers tunneling works already very well, and minority tunneling is still low enough to not result in significant recombination. Moreover, SiO 2 thickness up to maximum 1.6 nm is crucial to achieve high efficiency. Regarding rear geometry analysis, the efficiency curve as a function of emitter width peaks at 70% of pitch coverage. Further, it is shown that diffused dopants inside crystalline silicon make the device resilient to passivation quality. Finally, the calibrated model is used to perform an optimization study aiming at calculating the performance limit. The estimated performance limit is 27.3% for a 100-μm-thick bulk, 20-nm-thick poly-silicon layers, silver as rear contact, and double ARC. where he worked on advanced opto-electrical simulations of interdigitated back contacted solar cells. Since 2017, he has been with the Delft University of Technology as a Postdoctoral Researcher focusing on design and development of silicon heterojunction solar cells. His research interests include opto-electrical simulations and design of solar cells and semiconductor devices.Guangtao Yang received the Ph.D. degree from the Delft University of Technology, Delft, The Netherlands, in 2015, for his research on high-efficiency n-i-p thin-film silicon solar cells.Between 2015 and 2017, he was a Postdoctoral Researcher with the Delft University of Technology, focusing on poly-Si carrier-selective passivating contacts and their application in high-efficiency interdigital back-contacted c-Si solar cells. From January 2018 to June 2018, he was a Postdoctoral Researcher with the Eindhoven University of Technology. Since July 2018, he has been with the Delft University of Technology, working on carrier-selective passivating contacts based on poly-Si and its alloys, and transition metal-oxides.Olindo Isabella received the Ph.D. degree (cum laude) from the

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Advanced textured monocrystalline silicon substrates with high optical scattering yields and low electrical recombination losses for supporting crack‐free nano‐ to poly‐crystalline film growth

Vrijer

Smets

2021

Energy Science & Engineering

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Crystalline silicon tandem devices with perovskites, CIGS, and nanocrystalline silicon, as well as the TOPCon design, are incompatible with the conventional pyramidal surface texture of silicon. This is a result of crack formation in nano to polycrystalline growth on large sharp surface features. In this work, three texturing approaches are investigated, using alkaline and/or acidic wet chemical etches, that can lead to the crack‐free growth of nano to polycrystalline materials on textured surfaces. In this work, we show that without acidic smoothening, the fraction of <111> pyramidal surface coverage has to remain relatively small to prevent crack formation during crystalline growth on these surfaces. Applying an acidic etch as a function of time continuously smoothens surface features. This shifts the reflection to wider scattering angles and results in higher total reflected intensity with respect to the conventional texture, making it an interesting option for a wide variety of tandem pv applications. Finally, we demonstrate crater‐like features on a <100> monocrystalline silicon surface using an etching process including a sacrificial layer. These craters increase light scattering into wider angles, but to a lesser extent than the former approach. In terms of passivation, we demonstrate the positive effect of a post deposition hydrogen treatment. Initial dilution of the silane plasma improves passivation on a <111> surface, but is detrimental to passivation on a <100> surface, likely because the hydrogen dilution results in epitaxial growth at the c‐Si/a‐Si:H hetero‐interface. A minority carrier lifetime of over 3 ms has been achieved for all texturing approaches, after deposition of a 15 nm a‐Si:H layer on both sides of the wafer, for different a‐Si:H deposition and annealing schemes.

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IBC c-Si solar cells based on ion-implanted poly-silicon passivating contacts

Cited by 82 publications

References 20 publications

Simple processing of back-contacted silicon heterojunction solar cells using selective-area crystalline growth

Simple processing of back-contacted silicon heterojunction solar cells using selective-area crystalline growth

Numerical Simulations of IBC Solar Cells Based on Poly-Si Carrier-Selective Passivating Contacts

Advanced textured monocrystalline silicon substrates with high optical scattering yields and low electrical recombination losses for supporting crack‐free nano‐ to poly‐crystalline film growth

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