Crystalline silicon surface passivation by the negative-charge-dielectric Al&lt;inf&gt;2&lt;/inf&gt;O&lt;inf&gt;3&lt;/inf&gt;

Hoex, Bram; Schmidt, Jan; Sanden, M.C.M. van de; Kessels, W.M.M.

doi:10.1109/pvsc.2008.4922635

Cited by 13 publications

(9 citation statements)

References 16 publications

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“…The high negative fixed interface charges of the ALD-AlO x tunnel layer will accumulate holes at the c-Si interface, which will simultaneously enhance hole extraction probability and reduce surface recombination rates due to an efficient field-effect passivation in addition to the chemical passivation at the interface, as evident from the higher measured effective carrier lifetime (two orders of magnitude higher) than the passivation by either wet-SiO x or ozone-SiO x alone on symmetrically tunnel layer passivated n-type Cz wafers in our previous work [28]. These findings were consistent with literature for much thicker AlO x layers [35][36][37][38][39]. For hole-extracting capping layer materials, various candidates had been suggested, which includes highly p-doped polysilicon, transition metal oxide films with high work function such as molybdenum oxide (MoO x ) [40][41][42][43][44][45], tungsten oxide (WO x ), vanadium oxide (V 2 O 5 ), cuprous oxide (Cu 2 O) [46], or alternatively organic polymers, such as poly (3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) [47][48][49], among others.…”

Section: Introductionsupporting

confidence: 87%

Double-Sided Passivated Contacts for Solar Cell Applications: An Industrially Viable Approach Toward 24% Efficient Large Area Silicon Solar Cells

Ling¹,

Zhang²,

Wang³

et al. 2019

Silicon Materials

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Tunnel layer passivated contacts have been successfully demonstrated for next-generation silicon solar cell concepts, achieving improved device performance stemming from the significantly reduced contact recombination of the solar cell contacts. However, these carrier-selective passivated contacts are currently deployed only at the rear side of the silicon solar cell, while the front side adopts a conventional diffused junction and contacting scheme. In this work, we report on the novelty and feasibility of deploying tunnel layer passivated contacts on both sides of a silicon wafer-based solar cell, featuring a textured front surface and a planar rear surface. In particular, we demonstrate that silicon solar cells incorporating our in-house developed electron-selective thermal-SiO x /poly-Si(n +) and hole-selective thermal-SiO x /poly-Si(p +) passivated contacts have a solar cell efficiency potential approaching 24%. Deploying contact passivation only at the rear side of the solar cell, we have reached a solar cell efficiency of 21.7%, using conventional screen printing for metallization. We present a systematic approach of evaluating our in-house developed electron-selective and hole-selective passivated contacts on both textured and planar lifetime test structures, as well as dark I-V test structures, to extract the recombination current density j 0 and the contact resistance R c of the passivated contact, which is used for process optimization as well as for subsequent efficiency potential prediction. The two key challenges aiming at a double-sided integration of passivated contacts are (1) parasitic absorption within the front-side highly doped poly-Si capping layer, requiring the processing of ultrathin (≤10-nm) contact passivation layers. This has been quantified by numerical simulation (using SunSolve™) and also solved experimentally, i.e., processing ultrathin 3-/10-nm hole/electron extracting SiO x /poly-Si(p + /n +) passivated contact layers, reaching an implied open-circuit voltage of 690/703 mV on a planar/textured silicon surface, which will even further enhance after SiN x capping. (2) Ensuring process compatibility with conventional screen printing: Screen printing on electron extracting poly-Si(n +) seems feasible; however, screen printing on holeextracting poly-Si(p +) is still a challenge. Solar cell precursors have been processed, showing excellent pre-metallization results (implied-V OC $ 713 mV). According to 1 our efficiency potential prediction (using the measured j 0 and R c values of our developed contact passivation layers), bifacial double-sided passivated contact solar cells (efficiency potential of $23.2%, using our layers) can clearly outperform rearside-only passivated contact solar cells (efficiency potential of $22.5%).

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Section: Introductionsupporting

confidence: 87%

Double-Sided Passivated Contacts for Solar Cell Applications: An Industrially Viable Approach Toward 24% Efficient Large Area Silicon Solar Cells

Ling¹,

Zhang²,

Wang³

et al. 2019

Silicon Materials

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“…The improvement of the passivation quality after an annealing step has been widely reported [ 3 , 7 , 18 , 22 ], and it has been related to a lower D it ≤ 1 × 10 11 eV −1 cm −2 [ 17 ] combined with a higher concentration of fixed negative charges. The presence of these charges provides an electrostatic shielding due to a built-in electric field at the c-Si/Al 2 O 3 interface [ 4 , 23 ]. Here, we also see that textured substrates showed higher S eff values after the SiC x deposition.…”

Section: Resultsmentioning

confidence: 99%

Surface passivation and optical characterization of Al₂O₃/a-SiC_x stacks on c-Si substrates

López¹,

Ortega²,

Voz³

et al. 2013

Beilstein J. Nanotechnol.

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SummaryThe aim of this work is to study the surface passivation of aluminum oxide/amorphous silicon carbide (Al2O3/a-SiCx) stacks on both p-type and n-type crystalline silicon (c-Si) substrates as well as the optical characterization of these stacks. Al2O3 films of different thicknesses were deposited by thermal atomic layer deposition (ALD) at 200 °C and were complemented with a layer of a-SiCx deposited by plasma-enhanced chemical vapor deposition (PECVD) to form anti-reflection coating (ARC) stacks with a total thickness of 75 nm. A comparative study has been carried out on polished and randomly textured wafers. We have experimentally determined the optimum thickness of the stack for photovoltaic applications by minimizing the reflection losses over a wide wavelength range (300–1200 nm) without compromising the outstanding passivation properties of the Al2O3 films. The upper limit of the surface recombination velocity (S eff,max) was evaluated at a carrier injection level corresponding to 1-sun illumination, which led to values below 10 cm/s. Reflectance values below 2% were measured on textured samples over the wavelength range of 450–1000 nm.

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“…Corona charging experiments were performed to determine Q f [10]. As a positive charge was added stepwise to the film surface using a corona, the effective lifetime decreased until the positive charge was totally balanced with the negative fixed charge and then increased because the positive charge also enabled field-effect passivation.…”

Section: Methodsmentioning

confidence: 99%

Passivation mechanism of thermal atomic layer-deposited Al2O3 films on silicon at different annealing temperatures

et al. 2013

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Thermal atomic layer-deposited (ALD) aluminum oxide (Al2O3) acquires high negative fixed charge density (Qf) and sufficiently low interface trap density after annealing, which enables excellent surface passivation for crystalline silicon. Qf can be controlled by varying the annealing temperatures. In this study, the effect of the annealing temperature of thermal ALD Al2O3 films on p-type Czochralski silicon wafers was investigated. Corona charging measurements revealed that the Qf obtained at 300°C did not significantly affect passivation. The interface-trapping density markedly increased at high annealing temperature (>600°C) and degraded the surface passivation even at a high Qf. Negatively charged or neutral vacancies were found in the samples annealed at 300°C, 500°C, and 750°C using positron annihilation techniques. The Al defect density in the bulk film and the vacancy density near the SiOx/Si interface region decreased with increased temperature. Measurement results of Qf proved that the Al vacancy of the bulk film may not be related to Qf. The defect density in the SiOx region affected the chemical passivation, but other factors may dominantly influence chemical passivation at 750°C.

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Crystalline silicon surface passivation by the negative-charge-dielectric Al<inf>2</inf>O<inf>3</inf>

Cited by 13 publications

References 16 publications

Double-Sided Passivated Contacts for Solar Cell Applications: An Industrially Viable Approach Toward 24% Efficient Large Area Silicon Solar Cells

Double-Sided Passivated Contacts for Solar Cell Applications: An Industrially Viable Approach Toward 24% Efficient Large Area Silicon Solar Cells

Surface passivation and optical characterization of Al₂O₃/a-SiC_x stacks on c-Si substrates

Passivation mechanism of thermal atomic layer-deposited Al2O3 films on silicon at different annealing temperatures

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Crystalline silicon surface passivation by the negative-charge-dielectric Al<inf>2</inf>O<inf>3</inf>

Cited by 13 publications

References 16 publications

Double-Sided Passivated Contacts for Solar Cell Applications: An Industrially Viable Approach Toward 24% Efficient Large Area Silicon Solar Cells

Double-Sided Passivated Contacts for Solar Cell Applications: An Industrially Viable Approach Toward 24% Efficient Large Area Silicon Solar Cells

Surface passivation and optical characterization of Al2O3/a-SiCx stacks on c-Si substrates

Passivation mechanism of thermal atomic layer-deposited Al2O3 films on silicon at different annealing temperatures

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Surface passivation and optical characterization of Al₂O₃/a-SiC_x stacks on c-Si substrates