Heterojunction and Passivated Contacts: A Simple Method to Extract Both n/tco and p/tco Contacts Resistivity

Lachenal, D.; Baetzner, D. L.; Frammelsberger, W.; Legradic, B.; Meixenberger, J.; Papet, P.; Strahm, B.; Wahli, G.

doi:10.1016/j.egypro.2016.07.104

Cited by 32 publications

(14 citation statements)

References 4 publications

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“…The R TCO/a‐Si:H(p) decreases from 0.47 to 0.18 Ω·cm 2 as the oxygen partial pressure varies from 0.20 to 0.62 mTorr. These values of R TCO/a‐Si:H(p) are comparable with those previously reported values . This result means that the R TCO/a‐Si:H(p) can be effectively suppressed through enhancing the work function of rear TCO layer, which reduces the interface barrier and hence facilitates the carrier tunneling and/or thermionic emission process.…”

Section: Resultssupporting

confidence: 89%

Study and development of rear‐emitter Si heterojunction solar cells and application of direct copper metallization

Yang

Zhong

Zhang

et al. 2018

Progress in Photovoltaics

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We have presented a comprehensive study on the development of rear emitter silicon heterojunction (SHJ) solar cells, which shows more freedom for device optimization than the standard front emitter SHJ counterparts. The optimization of the p-type hydrogenated amorphous silicon (a-Si:H(p)) layer is liberated from the parasitic absorption issue, while the n-type hydrogenated amorphous silicon (a-Si:H(n)) layer is optimized considering the tradeoff between the light absorption loss and field-effect passivation. The front transparent conductive oxide (TCO) layer can be designed stressing on its optical properties because the lateral transport of the majority carriers at the front side of the cell is supported by the Si substrate, while the rear TCO layer is free to be tuned for suppressing the TCO/a-Si:H(p) contact resistance. A rear emitter SHJ solar cell (225.47 cm 2 ) fabricated by industry compatible process has been achieved with an efficiency of over 22%. We have further demonstrated the replacement of screen-printed silver metallization with a low cost direct copper metallization in the rear emitter SHJ solar cells. We report an exciting 22.06% cell efficiency which is comparable to that of the screen-printed counterpart.

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Section: Resultssupporting

confidence: 89%

Study and development of rear‐emitter Si heterojunction solar cells and application of direct copper metallization

Yang

Zhong

Zhang

et al. 2018

Progress in Photovoltaics

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“…Assuming an equal distribution of the resistances between both contacts (i.e. ,ℎ = , and , = ,ℎ )-a reasonable assumption, as shown by Lachenal et al32 -this corresponds to a summed majority-carrier contact resistance of ,ℎ + , = 3.3 Ω. cm 2 . For this device, ⁄ > 0.99, yet the power losses due to series resistance in the contacts amounts to about 5% in absolute value.…”

mentioning

confidence: 94%

Passivation, conductivity, and selectivity in solar cell contacts: Concepts and simulations based on a unified partial-resistances framework

Onno

Chen

Koswatta

et al. 2019

Journal of Applied Physics

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Passivation, conductivity, and selectivity are often acknowledged as the three requirements for optimal contacts to photovoltaic solar cells. Although there are generally accepted definitions and metrics for passivation and conductivity, a common understanding of the concept of selectivity is only now emerging. In this contribution, we present a generalized model of solar cell contacts based on the distinct lumped resistances encountered by electrons and holes traversing a contact, which we refer to as partial specific contact resistances. The relations between electron and hole partial current densities, quasi-Fermi level separation, and external voltage are derived from these partial specific contact resistances, leading to simple metrics for the aforementioned contact properties: the sum of the electron and hole resistances is a metric for passivation, their ratio a metric for selectivity, and the majority-carrier resistance a metric for conductivity. Using PC1D, we validate our model by simulating 10,500 cases of homojunction contacts to crystalline silicon solar cells, although our framework is material agnostic and can be equally applied to any other type of absorber. In these simulations, the hole contact and absorber are assumed to be ideal, whereas we vary the partial specific contact resistances in the electron contact by orders of magnitude by adjusting the electron and hole mobilities, their densities (through variations of the donor doping density), and the contact thickness. The simulations confirm the finding of the model that, when the contact fraction cannot be adjusted-as is the case with full-area contactscombined passivation and conductivity are necessary and sufficient for optimal solar cell performance, and they imply selectivity. However, the reciprocal is not true: contacts can be selective but lack conductivity-causing a deleterious drop in fill factor-or selective but provide poor passivation-leading to a reduction in implied open-circuit voltage and, hence, actual open-circuit voltage. Thus, selectivity is a meaningful metric in the sole case of partial-area contacts, where the contact fraction can be adjusted arbitrarily. I. INTRODUCTION Photovoltaic solar cells are devices that convert thermal radiation into electric power, in the form of a current of charge carriers that have a usable free energy corresponding to the difference in electrical potential between the two electrodes of the This is the author's peer reviewed, accepted manuscript. However, the online version of record will be different from this version once it has been copyedited and typeset.

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“…Usually, the contact at the front-side of SHJ front-junction devices is the p-contact. For this contact, values in the range of 300-500 mΩ cm 2 are given in literature [13,17,[28][29][30][31]. For the n-contact, lower values down to 50 mΩ cm 2 are given.…”

Section: Ii3 Specifics Of Front-vs Rear-junction Shj Devicesmentioning

confidence: 99%

“…• ρ c of the n-contact being lower than of the p-contact [13,17,[28][29][30], thus enabling better coupling,…”

Section: Ii3 Specifics Of Front-vs Rear-junction Shj Devicesmentioning

confidence: 99%

Lateral transport in silicon solar cells

Haschke

Christmann

Messmer

et al. 2020

Journal of Applied Physics

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Heterojunction and Passivated Contacts: A Simple Method to Extract Both n/tco and p/tco Contacts Resistivity

Cited by 32 publications

References 4 publications

Study and development of rear‐emitter Si heterojunction solar cells and application of direct copper metallization

Study and development of rear‐emitter Si heterojunction solar cells and application of direct copper metallization

Passivation, conductivity, and selectivity in solar cell contacts: Concepts and simulations based on a unified partial-resistances framework

Lateral transport in silicon solar cells

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