Wafer-Bonded GaInP/GaAs//Si Solar Cells With 30% Efficiency Under Concentrated Sunlight

Essig, Stephanie; Benick, Jan; Schachtner, Michael; Wekkeli, A.; Hermle, Martin; Dimroth, Frank

doi:10.1109/jphotov.2015.2400212

Cited by 88 publications

(48 citation statements)

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“…Elsewhere, we have the electron collector consisting of an a-Si:H(i)/Si:H(n)/Si:H(p) triple layer stack, which features an interband silicon tunnel junction (TJ) at the Si:H(n)/Si:H(p) interface. Notably, TJs are already successfully used in a variety of monolithic multi-junction solar cells [37][38][39][40][41][42] , and in our application we capitalize on this prior knowledge. The specific thin-film material requirements to achieve efficient interband-tunnelling passivating contacts for electrons are discussed in detail in the following section.…”

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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

et al. 2017

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“…This may be the case for perovskite on silicon [22] and also for III/V-cells on silicon, when wafer bonding or epitaxial growth is involved [18][19][20]. Therefore, the planar solar cell with sphere grating rear side presented in Section 3.3 could be a suitable bottom cell for such tandem structures.…”

Section: Estimates For Si-based Tandem Devicesmentioning

confidence: 99%

“…For a performance estimate of a III/V-silicon tandem device we refer to the recently published work of Essig et al [18]. They fabricated a triple junction device consisting of a GaInP/GaAs dual junction top cell that was wafer bonded onto a 280 mm thick silicon bottom cell.…”

Section: Iii/v On Siliconmentioning

confidence: 99%

“…The silicon bottom solar cell can only utilize the longer-wavelength part of the spectrum, which is weakly absorbed in silicon, thus necessitating efficient light trapping. Additionally, in many tandem concepts, for example wafer bonding [18] or direct III/V growth [19], the front side of the silicon cell is required to be planar and all the light trapping has to be realized at the rear. Silicon based tandem solar cells have been reported that are current-limited by the silicon cell [18,[20][21][22].…”

Section: Introductionmentioning

confidence: 99%

“…Additionally, in many tandem concepts, for example wafer bonding [18] or direct III/V growth [19], the front side of the silicon cell is required to be planar and all the light trapping has to be realized at the rear. Silicon based tandem solar cells have been reported that are current-limited by the silicon cell [18,[20][21][22]. Enhancing the current of the silicon cell will improve the current matching, thus leading to an overall higher current and efficiency.…”

Section: Introductionmentioning

confidence: 99%

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Rear side sphere gratings for improved light trapping in crystalline silicon single junction and silicon-based tandem solar cells

Eisenlohr

Lee

Benick

et al. 2015

Solar Energy Materials and Solar Cells

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Rear side hexagonal sphere gratings are demonstrated as diffractive structures that enhance the light path length in the near infrared, where crystalline silicon solar cells suffer from weak absorption. Moreover, the rear side sphere grating can be added behind a solar cell with flat rear surface, giving an “electrically flat but optically rough” device with high efficiency potential. Here, a thin passivating tunnel-contact layer electrically separates the sphere grating from the cell's base. Solar cells with the rear side sphere grating have obtained a VOC of up to 710 mV and a FF of up to 81.9%. External quantum efficiency measurements show a current density gain of 1.4 mA/cm2 due to the sphere grating. This leads to an overall efficiency of up to 22.1% for the solar cells with planar front side and rear side sphere grating. Estimates for perovskite–silicon and III/V-silicon tandem devices show that the efficiency of tandems can be enhanced by up to 2.4% absolute with a sphere grating on the rear side. Thus, sphere gratings could improve Si-based tandem devices that are limited due to a low current in the Si bottom cell

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CPV Multijunction Solar Cell Characterization

Osterwald

Siefer

2016

Handbook of Concentrator Photovoltaic Technology

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Wafer-Bonded GaInP/GaAs//Si Solar Cells With 30% Efficiency Under Concentrated Sunlight

Cited by 88 publications

References 18 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

Rear side sphere gratings for improved light trapping in crystalline silicon single junction and silicon-based tandem solar cells

CPV Multijunction Solar Cell Characterization

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