Junction Resistivity of Carrier-Selective Polysilicon on Oxide Junctions and Its Impact on Solar Cell Performance

Rienäcker, Michael; Bossmeyer, Marcel; Merkle, Agnes; Römer, Udo; Haase, Felix; Krügener, Jan; Brendel, Rolf; Peibst, Robby

doi:10.1109/jphotov.2016.2614123

Cited by 98 publications

(68 citation statements)

References 34 publications

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“…Figure shows the ion‐implanted and inkjet‐patterned IBC solar cells with POL y‐Si on O xide (POLO) junctions for both polarities (POLO‐IBC cells) with an active cell area of 7.6 × 15.5 mm, which we prepare following to the cell process described in the studies of Rienäcker et al . The p + POLO emitter and n + POLO base contact are separated by a 100‐μm wide textured trench region and form an interdigitated pattern with a pitch of 952 μm on the rear side of a saw‐damage etched 156 × 156 mm n ‐type Czochralski silicon wafer with a base resistivity of 4 Ωcm and a final thickness of 155 μm.…”

Section: Methodsmentioning

confidence: 99%

“…The p + POLO emitter and n + POLO base contact are separated by a 100‐μm wide textured trench region and form an interdigitated pattern with a pitch of 952 μm on the rear side of a saw‐damage etched 156 × 156 mm n ‐type Czochralski silicon wafer with a base resistivity of 4 Ωcm and a final thickness of 155 μm. The applied p + POLO and n + POLO junctions exhibit low contact resistivity of around 1 mΩcm 2 , while featuring excellent passivation qualities, resulting in a saturation current density J 0 of 4 and 2 fA/cm 2 per side, respectively …”

Section: Methodsmentioning

confidence: 99%

“…For measurement purposes, we deposit an aluminum front side grid with a finger distance of 1778 μm and a finger width of 240 μm through a shadow mask on top of the n + POLO front contact. The rear side is finished according to the study of Rienäcker et al …”

Section: Methodsmentioning

confidence: 99%

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Back‐contacted bottom cells with three terminals: Maximizing power extraction from current‐mismatched tandem cells

Rienäcker

Warren

Schnabel

et al. 2019

Progress in Photovoltaics

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Multi‐junction cells can significantly improve the energy yield of photovoltaic systems over a single‐junction cell. The internal interconnection scheme of the subcells is an important aspect in determining the resulting levelized cost of electricity. For a dual‐junction cell, two approaches are commonly discussed: series‐connected tandem cells with two terminals or independently working subcells in a four‐terminal (4T) tandem device. In this paper, we explore the working principle and the operation modes of a third, rarely discussed option: a three‐terminal (3T) tandem cell using a back‐contacted bottom cell with 3Ts. We use current–voltage measurements of illuminated 3T interdigitated back contact cells and confirm that the front and rear base contacts are at similar quasi‐Fermi level positions, which enables the bottom cell to either efficiently collect surplus carriers, in the case of a current‐limiting or carrier injecting top cell, or inject majority carriers, in the case of a current‐limiting bottom cell. As a result, no current matching is needed. The power output of an idealized 3T bottom cell without resistive effects is independent of the current density applied from the top cell. These characteristics of the 3T bottom cells enable a 3T tandem to operate as efficiently as a 4T tandem, while being compatible with monolithic design and not requiring intermediate grids. We propose a simple equivalent circuit model including additional resistive effects, which describes a real 3T bottom cell and achieves excellent agreement to the experiment. We deduce design guidelines for a 3T bottom cell in different operation regimes.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Back‐contacted bottom cells with three terminals: Maximizing power extraction from current‐mismatched tandem cells

Rienäcker

Warren

Schnabel

et al. 2019

Progress in Photovoltaics

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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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“…We vary the front surface recombination velocity and the surface recombination velocity at the interface of the c‐Si to the unimplanted region from 0.1 to 100 cm s −1 . We use the contact resistivity values measured in Rienacker et al The generation profile is simulated by Sunrays with the measured layer thicknesses as input parameter. The optical properties of poly‐Si are taken from Reiter et al Table lists the input parameters for the three analyzed solar cells.…”

Section: Methodsmentioning

confidence: 99%

26.1%‐efficient POLO‐IBC cells: Quantification of electrical and optical loss mechanisms

Hollemann

Haase

Schäfer

et al. 2019

Progress in Photovoltaics

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We present experimental results for interdigitated back contacted (IBC) solar cells with passivating POLO contacts for both polarities with a nominal intrinsic poly‐Si region between them. We reach efficiencies of 26.1% and 24.9% on a 1.3 Ω cm and 80 Ω cm p‐type FZ wafer and 24.6% on a 2 Ω cm n‐type Cz wafer, respectively. The initially measured implied efficiency potentials of the cells after passivating the surfaces are very similar, namely, 26.8%, 26.8%, and 26.4%, respectively. We attribute the difference between the efficiency potential and the final current‐voltage measurement to degradation, perimeter, and series and shunt resistance losses, which we quantify by lifetime measurements. With these measurements in combination with a finite element simulation, we determine the surface recombination velocity in the nominal intrinsic poly‐Si region to be in the range from 13 to 21 cm s−1. Using the same approach, we analyze the increase of the front surface recombination velocity during cell processing from 2 to 10 cm s−1 for the 1.3 Ω cm and from 0.5 to 2.3 cm s−1 for the 80 Ω cm. This leads to the fact that cells fabricated on lowly doped bulk material are more vulnerable to a process‐induced degradation of the surface passivation quality. We further determine the theoretical limits of the cells by firstly idealizing the recombination (28% for 1.3 Ω cm and 28.2% for 80 Ω cm) and secondly also idealizing the optics of the solar cells (29.4% and 29.5%).

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Junction Resistivity of Carrier-Selective Polysilicon on Oxide Junctions and Its Impact on Solar Cell Performance

Cited by 98 publications

References 34 publications

Back‐contacted bottom cells with three terminals: Maximizing power extraction from current‐mismatched tandem cells

Back‐contacted bottom cells with three terminals: Maximizing power extraction from current‐mismatched tandem cells

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

26.1%‐efficient POLO‐IBC cells: Quantification of electrical and optical loss mechanisms

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