A model of formation of fixed charge in thermal silicon dioxide

Александров, О. В.; Dus, A. I.

doi:10.1134/s1063782611040026

Cited by 13 publications

(12 citation statements)

References 30 publications

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“…18) This is in contrast to the wet-and ozone-SiO x tunnel layers, whereby Q f is approximately 1 order of magnitude lower. For comparison, literature data for other wet-chemically or thermally formed silicon oxide has been included as well [26][27][28][29][30][31] in Fig. 3(a).…”

Section: Resultsmentioning

confidence: 99%

Comparison and characterization of different tunnel layers, suitable for passivated contact formation

Ling

Zhang

et al. 2017

Jpn. J. Appl. Phys.

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Passivated contacts for solar cells can be realized using a variety of differently formed ultra-thin tunnel oxide layers. Assessing their interface properties is important for optimization purposes. In this work, we demonstrate the ability to measure the interface defect density distribution Dit(E) and the fixed interface charge density Qf for ultra-thin passivation layers operating within the tunnel regime (<2 nm). Various promising tunnel layer candidates [i.e., wet chemically formed SiOx, UV photo-oxidized SiOx, and atomic layer deposited (ALD) AlOx] are investigated for their potential application forming electron or hole selective tunnel layer passivated contacts. In particular, ALD AlOx is identified as a promising tunnel layer candidate for hole-extracting passivated contact formation, stemming from its high (negative) fixed interface charge density in the order of −6 × 1012 cm−2. This is an order of magnitude higher compared to wet chemically or UV photo-oxidized formed silicon oxide tunnel layers, while keeping the density of interface defect states Dit at a similar level (in the order of ∼2 × 1012 cm−2 eV−1). This leads to additional field effect passivation and therefore to significantly higher measured effective carrier lifetimes (∼2 orders of magnitude). A surface recombination velocity of ∼40 cm/s has been achieved for a 1.5 nm thin ALD AlOx tunnel layer prior to capping by an additional hole transport material, like p-doped poly-Si or PEDOT:PSS.

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Section: Resultsmentioning

confidence: 99%

Comparison and characterization of different tunnel layers, suitable for passivated contact formation

Ling

Zhang

et al. 2017

Jpn. J. Appl. Phys.

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“…Thickness gap, similar to the observation by Angermann et al [55] who observed a skewing toward the conduction band when p-type Si substrates are utilized. As compared to other thermally grown silicon oxides [56][57][58][59] which exhibited significantly lower D it values ($1-2 orders), their film thickness was however also significantly higher at $50-240 nm, making it inappropriate for tunnel layer applications. On the other hand, the wet-SiO x and ozone-SiO x tunnel oxides reported in Refs.…”

Section: Tunnel Oxidementioning

confidence: 88%

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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“…It is known, the effective surface charge of a sil icon wafer depends on charge of SES and traps in the oxide layer, as well as surface state. The sign of SES charge usually corresponds to one of major carriers, while the charge on traps in SiO 2 is usually positive [10,11]. In addition, the effective surface charge depends on the preliminary treatment and is negative after the peroxide-ammonia treatment (due to the attachment of OH groups on the SiO 2 surface) and becomes positive after PEI deposition (this positive charge is only partly compensated for by the charge of OH groups).…”

Section: Electrical Passivation Of Siliconmentioning

confidence: 99%