Dominant role of interfaces in solar cells with N-a-Si:H/P-c-Si heterojunction with intrinsic thin layer

Datta, A.; Damon-Lacoste, J.; Nath, M.; Cabarrocas, Pere Roca i; Chatterjee, P.

doi:10.1016/j.mseb.2008.10.017

Cited by 8 publications

(8 citation statements)

References 6 publications

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“…Modeling indicates that for improved performance of N-c-Si HIT cells, the valence band offset has to be reduced by a lower emitter band gap, unless the tunneling of holes takes place. Assuming that tunneling does not affect solar cell performance under one sun intensity, unless the band gap of P-a-Si: H Ն 1.90 eV ͑for reasons that will be discussed in the following͒, we agree with the observation of some other researchers 13,14 that the N-c-Si HIT cells having normal band gap P-a-Si:H emitter ͑E ͑P͒ϳ1.85 eV͒ are likely to have higher V oc 's ͑because of a more advantageous band diagram leading to higher V bi ͒, but lower FFs than P-c-Si:H HIT cells, at least the ones with a HJ at the emitter side only 17 due to this hole ͑majority carrier͒ accumulation ͓Fig. 5͑c͔͒.…”

Section: Sensitivity Of the Solar Cell Output To The P-layer Band supporting

confidence: 93%

“…Computer modeling of HIT structures has been carried out, not only to understand carrier transport in these structures, [12][13][14][15][16] but also to assess which HIT structure-whether on N-type or P-type c-Si substrate-is capable of attaining the higher efficiency. 13,14,17 In this article, we have used the detailed numerical electrical-optical model, Amorphous Semiconductor Device Modeling Program ͑ASDMP͒, 18,19 to trace the development of the Sanyo cells, beginning with their initial front HIT ͑with a heterojunction ͑HJ͒ only on the emitter side, and a conventional BSF layer, that is part of the c-Si wafer itself͒ solar cells, having rather low values of the open-circuit voltages ͑V oc ͒. 4 Their initial double HIT cells ͑where both the emitter and BSF layers are amorphous, and hence have HJs at either end of the c-Si wafer͒ also suffered from low V oc .…”

Section: Introductionmentioning

confidence: 99%

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Carrier transport and sensitivity issues in heterojunction with intrinsic thin layer solar cells on N-type crystalline silicon: A computer simulation study

Rahmouni¹,

Datta

Chatterjee

et al. 2010

Journal of Applied Physics

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Heterojunction with intrinsic thin layer or "HIT" solar cells are considered favorable for large-scale manufacturing of solar modules, as they combine the high efficiency of crystalline silicon ͑c-Si͒ solar cells, with the low cost of amorphous silicon technology. In this article, based on experimental data published by Sanyo, we simulate the performance of a series of HIT cells on N-type crystalline silicon substrates with hydrogenated amorphous silicon ͑a-Si:H͒ emitter layers, to gain insight into carrier transport and the general functioning of these devices. Both single and double HIT structures are modeled, beginning with the initial Sanyo cells having low open circuit voltages but high fill factors, right up to double HIT cells exhibiting record values for both parameters. The one-dimensional numerical modeling program "Amorphous Semiconductor Device Modeling Program" has been used for this purpose. We show that the simulations can correctly reproduce the electrical characteristics and temperature dependence for a set of devices with varying I-layer thickness. Under standard AM1.5 illumination, we show that the transport is dominated by the diffusion mechanism, similar to conventional P/N homojunction solar cells, and tunneling is not required to describe the performance of state-of-the art devices. Also modeling has been used to study the sensitivity of N-c-Si HIT solar cell performance to various parameters. We find that the solar cell output is particularly sensitive to the defect states on the surface of the c-Si wafer facing the emitter, to the indium tin oxide/P-a-Si:H front contact barrier height and to the band gap and activation energy of the P-a-Si:H emitter, while the I-a-Si:H layer is necessary to achieve both high V oc and fill factor, as it passivates the defects on the surface of the c-Si wafer. Finally, we describe in detail for most parameters how they affect current transport and cell properties.

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Section: Sensitivity Of the Solar Cell Output To The P-layer Band supporting

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Carrier transport and sensitivity issues in heterojunction with intrinsic thin layer solar cells on N-type crystalline silicon: A computer simulation study

Rahmouni¹,

Datta

Chatterjee

et al. 2010

Journal of Applied Physics

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“…These cells are therefore attractive as a high efficiency and low cost alternative to c-Si cells [1,2]. The performance of HIT solar cells is adversely affected by the defects (N ss ) on the wafer surface and good passivation of these defects is the key to attaining high efficiency [3,4] in these structures. Various models have been proposed to study the recombination via these amorphous-crystalline (a/c) interface defects based on their assumed nature [5][6][7].…”

Section: Introductionmentioning

confidence: 99%

“…For modeling these PL spectra we have used our detailed electrical-optical model "Amorphous Semiconductor Device Modeling Program (ASDMP)" [12,13], also capable of modeling c-Si and HIT cells [e.g. 3,4], by considering the N-type c-Si wafer to be in a HIT cell configuration with its surface coated by intrinsic a-Si:H layers before the addition of the amorphous emitter and back surface field (BSF) layers (Fig. 1b) on either end.…”

Section: Introductionmentioning

confidence: 99%

Photoluminescence spectrum from heterojunction with intrinsic thin layer solar cells: An efficient tool for estimating wafer surface defects

Datta¹,

Song²,

Wang³

et al. 2012

Journal of Non-Crystalline Solids

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“…11,12 In the case of solar cells, photovoltages are markedly influenced by the minority carrier lifetime. 13 Recombination of electron-hole pairs generated in the surface region proceeds at surface states, resulting in a decrease in the quantum efficiency of short-wavelength light, and thus in a decrease in the photocurrent density. 14 Recombination currents possess a large ideality factor, e.g., 2, 15 and thus, a fill factor is also decreased.…”

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confidence: 99%

Changes in Minority Carrier Lifetime of Hydrogen-Terminated Si Surfaces in Dry- and Wet-Air

Franco

Matsumoto

Kim

et al. 2012

ECS Solid State Letters

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Minority carrier lifetime of HF-treated Si(100) surfaces decreases in wet-air more rapidly than in dry-air. XPS measurements show that OH and O are mainly included in Si by keeping in wet-air and dry-air, respectively. OH cannot form network, and thus backbonded OH generates Si dangling bonds. On the other hand, backbonded O can form Si-O-Si networks, leading to the higher lifetime due to lower defect density. When the atmosphere is switched from dry-air to wet-air, the lifetime greatly decreases, and the workfunction increases. These changes are attributed to dominant formation of backbonded OH.Study on initial oxidation of Si is of importance not only from an academic viewpoint but also for application to semiconductor products such as solar cells and LSI. Semiconductor devices are usually fabricated using Si wafers after cleaning with the RCA method 1 followed by hydrofluoric acid (HF) etching. HF-etching forms ideal hydrogenterminated Si surfaces (i.e., only mono-hydride, Si-H) in the case of Si(111), 2 while mono-, di-(Si-H 2 ), and tri-(Si-H 3 ) hydride species are produced on technologically more important Si(100) surfaces. 3-5 HF-etched Si(100) surfaces with Si-H 2 and Si-H 3 are less stable in air than Si(111). Oxidation of HF-treated Si surfaces is enhanced by the presence of metal contaminants, more active species, defects, fluorineadsorbed sites, etc. 6,7 Initial oxidation of HF-treated Si surfaces were investigated using Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), Ultraviolet photoelectron spectroscopy (UPS), etc. 6-9 Chabal et al., 6 reported that when HFtreated Si(100) surfaces were kept in air, vibrational peaks due to SiH, SiH 2 , SiH(O) 3 , and SiH 2 (O) 2 were observed, indicating that O atoms occupied back-bonds with Si-H bonds remaining on Si surfaces. Hirose et al., 7 also concluded that oxygen attacked Si back-bonds and surface Si-H bonds were still present after the oxygen attack.The minority carrier lifetime strongly affects the electrical characteristics of semiconductor devices. 10 It is greatly decreased by the presence of defect states such as interface states. 11,12 In the case of solar cells, photovoltages are markedly influenced by the minority carrier lifetime. 13 Recombination of electron-hole pairs generated in the surface region proceeds at surface states, resulting in a decrease in the quantum efficiency of short-wavelength light, and thus in a decrease in the photocurrent density. 14 Recombination currents possess a large ideality factor, e.g., 2, 15 and thus, a fill factor is also decreased.In the present study, changes of minority carrier lifetime for HFtreated Si surfaces with time kept in air have been investigated. It is found that the minority carrier lifetime strongly depends on humidity, and concluded that hydroxyl species (OH) under the surfaces decreases the lifetime because the species does not form network, resulting in the production of defect states such as Si dangling bonds. ExperimentalPhosphorus-doped n-type Si(100...

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Dominant role of interfaces in solar cells with N-a-Si:H/P-c-Si heterojunction with intrinsic thin layer

Cited by 8 publications

References 6 publications

Carrier transport and sensitivity issues in heterojunction with intrinsic thin layer solar cells on N-type crystalline silicon: A computer simulation study

Carrier transport and sensitivity issues in heterojunction with intrinsic thin layer solar cells on N-type crystalline silicon: A computer simulation study

Photoluminescence spectrum from heterojunction with intrinsic thin layer solar cells: An efficient tool for estimating wafer surface defects

Changes in Minority Carrier Lifetime of Hydrogen-Terminated Si Surfaces in Dry- and Wet-Air

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