Current Losses at the Front of Silicon Heterojunction Solar Cells

Holman, Zachary C.; Descoeudres, Antoine; Barraud, Loris; Fernandez, F. Zicarelli; Seif, Johannes P.; Wolf, Stefaan De; Ballif, Christophe

doi:10.1109/jphotov.2011.2174967

Cited by 501 publications

(369 citation statements)

References 30 publications

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“…First, we compare the free-carrier absorption of an optimized front ITO layer 3,5 and an equivalent-resistance c-Si inversion layer to evaluate the potential short-circuit current gain in a TCO-free heterojunction solar cell. We chose a wavelength of 1000 nm where c-Si is still absorbing and free-carrier absorption begins to occur.…”

Section: Resultsmentioning

confidence: 99%

“…Note that widening the bandgap of the emitter and front intrinsic a-Si:H layers would also decrease the UV and visible parasitic absorption in these layers. 3 The simulated sheet resistance of the inversion layer is shown in Figure 5. The sheet resistance was calculated according to the following equation:…”

Section: Resultsmentioning

confidence: 99%

“…With stacks of intrinsic and doped a-Si:H layers, excellent surface passivation can be achieved, leading to high open-circuit voltages in excess of 720 mV. 1,2 The drawback of the amorphous emitter is its low mobility, which, together with a thickness limited to a few nanometers to reduce light absorption losses, 3,4 results in a high resistivity. To overcome this disadvantage and achieve high efficiencies, a transparent conductive oxide (TCO) layer is required on top of the emitter for lateral transport of photogenerated charge carriers to metal finger contacts; the TCO also serves as a single-layer antireflection coating.…”

Section: Introductionmentioning

confidence: 99%

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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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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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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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“…3 shows the optical absorbances measured by spectrophotometry, subtracting the contribution of the glass slide. By comparing with a-Si:H (calculated from extinction coefficient data [35]), all three oxides are less absorbent up to ~600 nm in wavelength, while MoO x is the most transparent. In parallel, electrical measurements of the oxide films at room temperature yielded rather low lateral conductivities (σ V2Ox ~8 x10 -8 S/cm, σ MoOx ~1.8 x10 -7 S/cm and σ WOx ~1.1 x10 -7 S/cm) in accordance with previous reports [9,18].…”

Section: Properties Of Transition Metal Oxidesmentioning

confidence: 99%

Transition metal oxides as hole-selective contacts in silicon heterojunctions solar cells

Gerling

Mahato

Morales-Vilches

et al. 2016

Solar Energy Materials and Solar Cells

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This work reports on a comparative study comprising three transition metal oxides, MoO 3 , WO 3 and V 2 O 5 , acting as front p-type emitters for n-type crystalline silicon heterojunction solar cells. Owing to their high work functions (>5 eV) and wide energy band gaps, these oxides act as transparent hole-selective contacts with semiconductive properties that are determined by oxygen-vacancy defects (MoO 3-x ), as confirmed by x-ray photoelectron spectroscopy. In the fabricated hybrid structures, 15 nm thick transition metal oxide layers were deposited by vacuum thermal evaporation. Of all three devices, the V 2 O 5 /n-silicon heterojunction performed the best with a conversion efficiency of 15.7% and an open-circuit voltage of 606 mV, followed by MoO 3 (13.6%) and WO 3 (12.5%). These results bring into view a new silicon heterojunction solar cell concept with advantages such as the absence of toxic dopant gases and a simplified low-temperature fabrication process.

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“…The amorphous nature of a-Si:H leads to a low conductivity and high recombination rate of electron-holes pairs that are generated in the emitter, which limits the conversion of light at short wavelengths. [2,3] To leverage the progresses made in heterojunction solar cells while overcoming these limitations, it would be interesting to integrate new materials as front emitter, with a higher transparency, higher conductivity, and lower recombination rate.…”

Section: Introductionmentioning

confidence: 99%