&gt;21% Efficient Silicon Heterojunction Solar Cells on n- and p-Type Wafers Compared

Descoeudres, Antoine; Holman, Zachary C.; Barraud, Loris; Morel, S.; Wolf, Stefaan De; Ballif, Christophe

doi:10.1109/jphotov.2012.2209407

Cited by 196 publications

(135 citation statements)

References 31 publications

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“…The higher surface recombination evident on the p þ surface relative to the n þ is potentially due to c-Si/a-Si:H(i) interface defects exhibiting an electron to hole capture cross section area ratio (r n /r p ) greater than unity. 23 …”

Section: A Interface Passivationmentioning

confidence: 99%

Amorphous silicon passivated contacts for diffused junction silicon solar cells

Bullock

Yan

Wan

et al. 2014

Journal of Applied Physics

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Carrier recombination at the metal contacts is a major obstacle in the development of high-performance crystalline silicon homojunction solar cells. To address this issue, we insert thin intrinsic hydrogenated amorphous silicon [a-Si:H(i)] passivating films between the dopant-diffused silicon surface and aluminum contacts. We find that with increasing a-Si:H(i) interlayer thickness (from 0 to 16 nm) the recombination loss at metal-contacted phosphorus (n+) and boron (p+) diffused surfaces decreases by factors of ∼25 and ∼10, respectively. Conversely, the contact resistivity increases in both cases before saturating to still acceptable values of ∼ 50 mΩ cm2 for n+ and ∼100 mΩ cm2 for p+ surfaces. Carrier transport towards the contacts likely occurs by a combination of carrier tunneling and aluminum spiking through the a-Si:H(i) layer, as supported by scanning transmission electron microscopy–energy dispersive x-ray maps. We explain the superior contact selectivity obtained on n+ surfaces by more favorable band offsets and capture cross section ratios of recombination centers at the c-Si/a-Si:H(i) interface.

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Section: A Interface Passivationmentioning

confidence: 99%

Amorphous silicon passivated contacts for diffused junction silicon solar cells

Bullock

Yan

Wan

et al. 2014

Journal of Applied Physics

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“…With the data for c-Si from Table I, the surface defect density (neglecting the field-effect passivation) results in a surface recombination velocity of 1 cm/s and an effective lifetime of 3.7 ms, consistent with regularly measured lifetimes. 25 ITO was modeled as a conductor that contributed only to the series resistance; we neglected other effects like band bending and band-to-band tunneling. 30 The thickness of the ITO was 65 nm and its mobility and free-carrier concentration are 30 cm 2 /(Vs) and 3 Â 10 20 cm À3 , respectively, giving it a sheet resistance of 107 X/sq.…”

Section: Experimental and Simulationsmentioning

confidence: 99%

“…Such cells would feature an improved blue and red response, be potentially cheaper, and avoid passivation layer damage related to TCO sputtering, 24 compared to our standard devices. 25 When the TCO is absent, the a-Si:H emitter is too resistive to contribute noticeably to the lateral conductivity and has the same role as the insulator in metal-insulatorsemiconductor solar cells of inducing an inversion layer in c-Si. However, while in metal-insulator-semiconductor solar cells, the inversion layer is induced by fixed surface charges, the inversion layer in a-Si:H/c-Si solar cells is a consequence of the a-Si:H emitter doping and the band discontinuities at the interface, introducing new parameters to alter the conductivity of the inversion layer.…”

Section: Introductionmentioning

confidence: 99%

Analysis of lateral transport through the inversion layer in amorphous silicon/crystalline silicon heterojunction solar cells

Filipič

Holman

Smole

et al. 2013

Journal of Applied Physics

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In amorphous/crystalline silicon heterojunction solar cells, an inversion layer is present at the front interface. By combining numerical simulations and experiments, we examine the contribution of the inversion layer to lateral transport and assess whether this layer can be exploited to replace the front transparent conductive oxide (TCO) in devices. For this, heterojunction solar cells of different areas (2 Â 2, 4 Â 4, and 6 Â 6 mm 2 ) with and without TCO layers on the front side were prepared. Laser-beam-induced current measurements are compared with simulation results from the ASPIN2 semiconductor simulator. Current collection is constant across millimeter distances for cells with TCO; however, carriers traveling more than a few hundred microns in cells without TCO recombine before they can be collected. Simulations show that increasing the valence band offset increases the concentration of holes under the surface of n-type crystalline silicon, which increases the conductivity of the inversion layer. Unfortunately, this also impedes transport across the barrier to the emitter. We conclude that the lateral conductivity of the inversion layer may not suffice to fully replace the front TCO in heterojunction devices. V C 2013 AIP Publishing LLC.

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“…14 carrier lifetimes (up to the millisecond range), no light-induced degradation caused by boron-oxygen pair, and high impurity tolerance. [16][17][18][19][20][21] Despite the great success in developing high performance SHJ devices, a large number of photons are still wasted, leading to the significant power loss. It is reported that the total power loss is more than 20% of the current output power.…”

mentioning

confidence: 99%

“…The optical improvement due to the downconversion effect of GQDs gives rise to a high efficiency of 16 for the wavelengths ranging from 300 to 1000 nm.…”

mentioning

confidence: 99%

Efficiency Enhancement of Silicon Heterojunction Solar Cells via Photon Management Using Graphene Quantum Dot as Downconverters

et al. 2015

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By employing graphene quantum dots (GQDs), we have achieved a high efficiency of 16.55% in n-type Si heterojunction solar cells. The efficiency enhancement is based on the photon downconversion phenomenon of GQDs to make more photons absorbed in the depletion region for effective carrier separation, leading to the enhanced photovoltaic effect. The short circuit current and the fill factor are increased from 35.31 to 37.47 mA/cm2 and 70.29% to 72.51%, respectively. The work demonstrated here holds the promise for incorporating graphene-based materials in commercially available solar devices for developing ultrahigh efficiency photovoltaic cells in the future.

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>21% Efficient Silicon Heterojunction Solar Cells on n- and p-Type Wafers Compared

Cited by 196 publications

References 31 publications

Amorphous silicon passivated contacts for diffused junction silicon solar cells

Amorphous silicon passivated contacts for diffused junction silicon solar cells

Analysis of lateral transport through the inversion layer in amorphous silicon/crystalline silicon heterojunction solar cells

Efficiency Enhancement of Silicon Heterojunction Solar Cells via Photon Management Using Graphene Quantum Dot as Downconverters

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