Raising the one-sun conversion efficiency of III–V/Si solar cells to 32.8% for two junctions and 35.9% for three junctions

Essig, Stephanie; Allebé, Christophe; Remo, Timothy; Geisz, John F.; Steiner, Myles A.; Horowitz, Kelsey; Barraud, Loris; Ward, Jas S.; Schnabel, Manuel; Descoeudres, Antoine; Young, David L.; Woodhouse, Michael; Despeisse, Matthieu; Ballif, Christophe; Tamboli, Adele C.

doi:10.1038/nenergy.2017.144

Cited by 483 publications

(425 citation statements)

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“…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 . For a dual‐junction tandem solar cell, bottom cells based on Si wafer technology are an excellent choice thanks to an ideal bandgap of Si of 1.1 eV, its earth‐abundancy and non‐toxicity, its highly developed and cost‐competitive manufacturing technology, high efficiency, and market‐dominance .…”

Section: Introductionmentioning

confidence: 99%

“…While much research has focused on achieving better performance through optimized subcells, the internal interconnection of tandem solar cells, the associated number of terminals, the corresponding cell architecture, and the module and system integration scheme, are also of great importance. These aspects determine the efficiency and annual energy yield of a photovoltaic system .…”

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: Introductionmentioning

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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“…Best reported efficiencies under AM1.5G illumination of (A) single‐junction PV cells with different absorbers and (B) a selection of tandem PV cells . All efficiencies are certified except for the 160‐cm 2 perovskite, the perovskite/perovskite tandems, the perovskite/silicon tandems with area > 1 cm 2 , and the module presented in this work.…”

Section: Introductionmentioning

confidence: 96%

“…However, constrained by the current and lattice mismatch between GaAs and silicon, GaAs/Si tandems have been successful only in four‐terminal configurations. Essig et al demonstrated a record 32.8%‐efficient GaAs/Si tandem device, 1 cm 2 in size, by mechanically stacking a GaAs cell on top of a silicon heterojunction cell; similarly, Rienacker et al reported a 1.1‐cm 2 , 31.5%‐efficient GaAs/Si tandem but with a silicon IBC cell . Substituting their GaAs cells with GaInP/GaAs dual‐junction cells, both groups reported >35% efficiency.…”

Section: Introductionmentioning

confidence: 99%

GaAs/silicon PVMirror tandem photovoltaic mini‐module with 29.6% efficiency with respect to the outdoor global irradiance

Fisher

Meng

et al. 2019

Progress in Photovoltaics

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Balance‐of‐system costs now dominate the installed cost of photovoltaic systems, causing the annually averaged module efficiency to become a primary system cost driver. The resulting continued push towards higher module efficiencies, coupled with the dominance of single‐axis tracking in the utility‐scale PV market, may create an opportunity for a low‐concentration tandem module technology. Here, we demonstrate such a tandem, using the “PVMirror” concept, on the mini‐module scale. The tandem couples a (concentrating) silicon PVMirror having an aperture area of 156.25 cm2 with a gallium arsenide receiver to achieve 29.6% efficiency with respect to the outdoor global irradiance. Unlike most concentrating technologies, the silicon PVMirror collects some of the diffuse light, but the tandem would nevertheless achieve 31% efficiency in the absence of diffuse light, as in a laboratory measurement. The same tandem technology can be implemented with a wide‐bandgap thin‐film PVMirror and silicon receiver—a potentially cost‐competitive combination—when efficient wide‐bandgap cells have been developed.

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“…The extensive studies on Si-based photoelectrodes for PEC energy conversion applications over the last few decades [25] have led to development and demonstration of successful protection strategies for Si-based photoelectrodes in contact with aqueous electrolytes. Moreover, as a small bandgap semiconductor (1.1 eV), silicon shows great promises as the bottom layer material for tandem junction solar cells, such as a-Si/µc-Si (amorphous Si/microcrystalline Si) tandem cell [26] and III-V/Si tandem cell, [27] which features not only higher efficiency but also larger photovoltage. [20] This bodes well for SFBs, because the simplified photoelectrode structure without catalysts in SFBs and the less harsh neutral pH condition are expected to further extend the lifetime of Si photoelectrodes.…”

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confidence: 99%

A Long Lifetime Aqueous Organic Solar Flow Battery

Kerr

Goulet

et al. 2019

Advanced Energy Materials

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The monolithic integration of solar energy conversion and electrochemical energy storage offers a practical solution to provide uninterruptable power supply on demand regardless of the ebb and flow of solar irradiation. Although connecting photovoltaics (PVs) with batteries, as adopted by some solar farms nowadays, [1] can provide the same uninterrupted power supply, the high capital cost and large footprint of two separate devices limit the market cases feasible for this option. [2] In contrast, integrated solar energy conversion and storage may represent a more compact, efficient, and cost-effective approach for off-grid electrification. [3] Among the many different types of "solar rechargeable battery" devices that have been reported [3,4] since the first demonstration in 1976, [5] integrated solar flow batteries (SFBs) hold great promises for practical applications because the solar component shares the same liquid electrolyte as the energy storage component, [6] which is based on redox flow batteries (RFBs) and can be easily scaled up. [2b] Despite the significant progress, most of such integrated devices suffer from some common scientific and technical issues. [4a,7] The first question one typically asks about any "solar device" is the efficiency. Due to the intrinsic efficiency limits of the solar energy conversion components and the working voltage mismatch between the solar energy conversion component and electrochemical energy storage component, the round-trip efficiency (i.e., solar-to-output electricity efficiency, SOEE) of most previously reported solar rechargeable devices rarely exceeded 5%. [3a,4a,7,8] It was recently demonstrated that by monolithically integrating III-V tandem junction solar cells with properly voltage matched RFBs, the integrated SFB device can deliver a SOEE of 14.1%. [9] Importantly, this comprehensive study [9] also revealed a set of general design principles that can further boost the SFB's efficiency. Primary among them is that the formal potential difference of selected redox couples needs to be closely matched with the photovoltage of the photoelectrodes at the maximum power point. Although III-V tandem junction solar cells can enable unprecedented high SOEE, the manufacturing cost for them ($40 W −1 to over $100 W −1 ) [10] is too high for practical applications. The most widely produced crystalline silicon-based solar cells have the cost of $0.15 to $0.25 W −1 after decades of research and commercial deployment, [10] thus are a good candidate for practical SFBs owing to its high abundance and decent PV efficiency.Monolithically integrated solar flow batteries (SFBs) hold promise as compact stand-alone energy systems for off-grid solar electrification. Although considerable research is devoted to studying and improving the round-trip efficiency of SFBs, little attention is paid to the device lifetime. Herein, a neutral pH aqueous electrolyte SFB with robust organic redox couples and inexpensive silicon-based photoelectrodes is demonstrated. Enabled by the excellent ...

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Raising the one-sun conversion efficiency of III–V/Si solar cells to 32.8% for two junctions and 35.9% for three junctions

Cited by 483 publications

References 45 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

GaAs/silicon PVMirror tandem photovoltaic mini‐module with 29.6% efficiency with respect to the outdoor global irradiance

A Long Lifetime Aqueous Organic Solar Flow Battery

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