Laser contact openings for local poly-Si-metal contacts enabling 26.1%-efficient POLO-IBC solar cells

Haase, Felix; Hollemann, Christina; Schäfer, Sören; Merkle, Agnes; Rienäcker, Michael; Krügener, Jan; Brendel, Rolf; Peibst, Robby

doi:10.1016/j.solmat.2018.06.020

Cited by 529 publications

(367 citation statements)

References 22 publications

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“…Bottom cells for highly efficient BJT type tandem cells should be designed similar to high efficiency IBC single junction solar cells with low R IBC values . Large‐scale industrial‐type IBC cells with a total series resistance of 400 mΩcm 2 and an efficiency of 25.2% as reported by Smith et al are an excellent choice for industrialization of BJT type tandem cells.…”

Section: Implications For 3t Tandem Solar Cellsmentioning

confidence: 99%

“…Steady improvements over decades have led to the exceptional success of market‐dominating silicon‐based photovoltaics and recently enabled the demonstration of record efficiencies for interdigitated back contact (IBC) silicon solar cells, close to the theoretical limit of 29.6% . Splitting the spectrum through multiple junctions that are stacked optically in series in a multi‐junction cell (or tandem cell) has been demonstrated to further increase the cell efficiency significantly .…”

Section: Introductionmentioning

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: Implications For 3t Tandem Solar Cellsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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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“…To passivate the front side, an atomic layer deposited (ALD) AlO x layer and a plasma‐enhanced chemical vapor deposited (PECVD) SiN y /SiO z layer stack is applied. On the rear side, we define the contact area by laser contact opening (LCO) . Finally, the cell is metallized by a 10‐μm‐thick evaporated aluminum layer and a sputtered SiO z layer.…”

Section: Methodsmentioning

confidence: 99%

“…With this concept, we so far achieve an independently certified efficiency of 26.10 ± 0.31% on p ‐type, 1.3 Ω cm material . However, the efficiency potential of these cells—as experimentally determined by injection‐dependent infrared lifetime mapping (ILM) on the cell precursors during cell processing—is significantly higher.…”

Section: Introductionmentioning

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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“…Zum anderen werden zunehmend Siliziumoxid-passivierte Solarzellen mit Kontaktschichten aus poly-Silizium als nächste große Weiterentwicklung angesehen [11]. Hier sind das POLO-Konzept des ISFH (26,1 % Effizienz) [12] sowie TopCon des Fraunhofer ISE (25,7 % Effizienz) [13,14] …”

Section: Abbildung 6: Elektronenstrahlverdampfte Siliziumschicht Auf unclassified

Elektronenstrahlverdampfen von Silizium

Amkreutz

Muske²

2019

Vak Forsch Prax

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Summary Electron beam evaporation of silicon High rate electron beam evaporation of silicon is a versatile technique to deposit silicon layers with tailored properties on large areas in a cost effective manner. A unique feature of the process is the wide range of deposition rates that can be selected. This technique allows for the deposition of nanometer thin layers with high reproducibility on the one hand, on the other hand layers with thicknesses of several tens of micrometers and low film stress can be deposited within minutes. Due to the high quality of the deposited silicon it is possible to form ultra‐thin layers as contacts in solar cells or for TFT applications or several 10 micrometer thick films as absorbers in LPC solar cells or as “construction” material for MEMS. This article reports on the deposition process, the material properties and illustrates the applicability based on examples from our current research activities.

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Laser contact openings for local poly-Si-metal contacts enabling 26.1%-efficient POLO-IBC solar cells

Cited by 529 publications

References 22 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

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

Elektronenstrahlverdampfen von Silizium

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