Contact Resistivity of the p-Type Amorphous Silicon Hole Contact in Silicon Heterojunction Solar Cells

Leilaeioun, Mehdi; Weigand, William A.; Boccard, Mathieu; Yu, Zhengshan J.; Fisher, Kathryn C.; Holman, Zachary C.

doi:10.1109/jphotov.2019.2949430

Cited by 37 publications

(15 citation statements)

References 60 publications

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“…The minimum c of 104 m.cm 2 is obtained with the thinnest VOx (4.5 nm), comparable to that of the best reported a-Si:H/a-Si:H(p) contact ( 100 m.cm 2 ) in conventional SHJ device. [44] Note that the c extracted here should be considered as the upper limit value for the VOx/p-Si and VOx/a-Si:H/p-Si heterocontacts, because it consists of the resistance of the front VOx/p-Si and rear p-Si/Al interfaces, as well as the bulk resistivity of VOx and a-Si:H. Therefore, these c values should meet the threshold ( 100 m.cm 2 ) for a full-area contact required to make high efficiency c-Si solar cells. [45] Figure 4b shows the dependence of the c of the VOx/p-Si heterocontacts on temperature, which was measured on a probe station with an integrated heating system.…”

Section: Resultsmentioning

confidence: 99%

Atomic Layer Deposition of Vanadium Oxide as Hole‐Selective Contact for Crystalline Silicon Solar Cells

Yang

Liu

et al. 2020

Adv Elect Materials

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High carrier recombination loss at the contact regions has become the dominant factor limiting the power conversion efficiency (PCE) of crystalline silicon (c‐Si) solar cells. Dopant‐free carrier‐selective contacts are being intensively developed to overcome this challenge. In this work, vanadium oxide (VOx) deposited by atomic layer deposition (ALD) is investigated and optimized as a potential hole‐selective contact for c‐Si solar cells. ALD VOx films are demonstrated to simultaneously offer a good surface passivation and an acceptable contact resistivity (ρc) on c‐Si, achieving a best contact recombination current density (J0) of ≈40 fA cm−2 and a minimum ρc of ≈95 mΩ.cm2. Combined with a high work function of 6.0 eV, ALD VOx films are proven to be an effective hole‐selective contact on c‐Si. By the implementation of hole‐selective VOx contact, the state‐of‐the‐art PCE of 21.6% on n‐type c‐Si solar cells with a high stability is demonstarted. These results demonstrate the high potential of ALD VOx as a stable hole‐transport layer for photovoltaic devices, with applications beyond c‐Si, such as perovskite and organic solar cells.

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Section: Resultsmentioning

confidence: 99%

Atomic Layer Deposition of Vanadium Oxide as Hole‐Selective Contact for Crystalline Silicon Solar Cells

Yang

Liu

et al. 2020

Adv Elect Materials

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“…However, significant engineering advances in electronic properties to lower the VB edge energy farther from vacuum (increase E VB ), while maintaining high doping and low D it , could push the performance higher into the blue region. This compares with (p) a-Si:H (gray dotted circles) doped to approximately 10 19 cm −3 [44] with a combined doping and alignment leading to high electronic performance and efficiencies of 25.4%, regardless of D it . Since (p) a-Si:H has ideal N A and E VB , these contacts have a higher D it tolerance than NiO x .…”

Section: A Simulated Sensitivity Of Materials Parametersmentioning

confidence: 92%

Evaluating Materials Design Parameters of Hole-Selective Contacts for Silicon Heterojunction Solar Cells

Woods‐Robinson¹,

Fioretti²,

Haschke³

et al. 2021

IEEE J. Photovoltaics

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Silicon heterojunction (SHJ) solar cell efficiencies are limited by parasitic absorption from the hydrogenated amorphous silicon (a-Si:H) front contact, but this may be mitigated by selecting an alternative carrier selective contact material with a wider band gap. When choosing such a material as the hole-selective contact ("p-layer"), the alignment of the material's valence band edge energy (E VB ) with that of crystalline silicon (c-Si) is an important criterion, but several other material parameters can also influence the band bending at the contact interface. In this article, we simulate an (n)c-Si/(i)a-Si:H/p-layer interface to explore the influence of six materials parameters in a variable p-layer on the SHJ performance. We find a strong influence on the fill factor (FF) from thickness, doping, and E VB ,and on V OC from the interfacial defect density; notably, optimal E VB is ∼0.1 eV higher than the valence band edge energy of a-Si:H. Multiparameter sensitivity analyses demonstrate how performance is simultaneously influenced by E VB and doping; thus, both parameters should be optimized alongside one another. To assess the influence of these parameters experimentally, we grow p-type NiO x as a test-case p-layer, which shows that FFs decrease

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“…A low ρ c at the TCO/a-Si:H and a-Si:H/c-Si heterojunctions can be reached by sufficient a-Si:H net doping [3], [9], [22]. The net doping of amorphous silicon is defined by the dopant concentration and the doping efficiency, which is reduced by defect creation [23]- [25].…”

Section: B A-si:h Doping Variationmentioning

confidence: 99%

“…However, electrical and optical properties are closely linked. A high carrier concentration, e.g., leads to a higher lateral conductivity [6] and a lower contact resistivity [9], [10] while reducing the transparency. Thus, high transparency has to be balanced with high conductivity, e.g., via tuning the TCO oxygen (O 2 ) content [11].…”

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confidence: 99%

“…One way to relax the constraints on TCO optimization are high-mobility TCOs with μ TCO > 100 cm 2 /Vs allowing the reduction of the charge carrier concentration N TCO for higher transparency while maintaining a high lateral conductivity [12]. Another option is to utilize layer stacks to decouple the required properties at the interface from the bulk layer [9], [13], [14].…”

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confidence: 99%

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Influence of TCO and a-Si:H Doping on SHJ Contact Resistivity

Luderer

Tutsch

Messmer

et al. 2021

IEEE J. Photovoltaics

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Resistive losses in silicon heterojunction (SHJ) solar cells are partly linked to transport barriers at the amorphous silicon/crystalline silicon (a-Si:H/c-Si) and transparent conductive oxide (TCO)/a-Si:H interfaces. A key parameter is the position of the Fermi-level on either side of the junction which we modify by a systematic doping variation of the amorphous silicon and the transparent conductive oxide. We identify the charge carrier concentration to be the main driver for low contact resistance. For a-Si:H, this is achieved by using a sufficient but not too high doping gas concentration during deposition. For indium tin oxide (ITO) and aluminum zinc oxide (AZO), no or only a very low oxygen (O 2 ) gas concentration during deposition is needed. We show that a stack of low-oxygen ITO interlayer and an oxygen-rich ITO "bulk" layer is not only an effective means to combine efficient transport and low TCO absorption but also to improve the thermal stability of the a-Si:H/TCO/metal contact resistivity (ρ c ). Such a layer stack helps to relax the constraints regarding the optoelectrical performance and improves the efficiency of SHJ solar cells.

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Contact Resistivity of the p-Type Amorphous Silicon Hole Contact in Silicon Heterojunction Solar Cells

Cited by 37 publications

References 60 publications

Atomic Layer Deposition of Vanadium Oxide as Hole‐Selective Contact for Crystalline Silicon Solar Cells

Atomic Layer Deposition of Vanadium Oxide as Hole‐Selective Contact for Crystalline Silicon Solar Cells

Evaluating Materials Design Parameters of Hole-Selective Contacts for Silicon Heterojunction Solar Cells

Influence of TCO and a-Si:H Doping on SHJ Contact Resistivity

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