Laser Assisted Patterning of a-Si:H: Detailed Investigation of Laser Damage

Xu, Menglei; Bearda, Twan; Radhakrishnan, Hariharsudan Sivaramakrishnan; Filipič, Miha; Gordon, Ivan; Debucquoy, Maarten; Szlufcik, Jozef; Poortmans, Jef

doi:10.1002/pssr.201700125

Cited by 5 publications

(6 citation statements)

References 19 publications

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“…To quantify the impact of laser damage on p + /i a-Si:H/c-Si passivation quality, uncalibrated PL images are taken and the minority carrier lifetimes (τ) are recorded using QSSPC after p + /i a-Si:H passivation and after laser ablation, respectively. Results of a-Si:H/SiOx samples have been discussed in detail by us previously [38]. Comparing Figure 5 a) and 5 b), an p + /i a-Si:H/c-Si passivation degradation is observed for the DBR device sample processed at a laser speed of 0.7 m/s due to laser damage in OZs.…”

Section: Process Flow Of Shj-ibc Solar Cellmentioning

confidence: 58%

“…roughness, thermal damage) is present not only in OZs but also in the regions irradiated by one laser pulse. Detailed investigation using transmission electron microscopy has been reported by us elsewhere [38]. In short, more severe laser damage is observed in OZs with respect to the regions irradiated by only one laser pulse.…”

Section: Process Flow Of Shj-ibc Solar Cellmentioning

confidence: 93%

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Simple emitter patterning of silicon heterojunction interdigitated back-contact solar cells using damage-free laser ablation

Bearda

Filipič

et al. 2018

Solar Energy Materials and Solar Cells

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In early 2017, the world record efficiency for single-junction crystalline silicon (c-Si) solar cells was achieved by merging amorphous silicon (a-Si:H)/c-Si heterojunction technology and back-contact architecture. However, to fabricate such silicon heterojunction interdigitated back-contact (SHJ-IBC) solar cells, complex a-Si:H patterning steps are required to form the interdigitated a-Si:H strips at the back side of the devices. This fabrication complexity raises concerns about the commercial potential of such devices. In this work, a novel process scheme for a-Si:H patterning using damage-free laser ablation is presented, leading to a fast, simple and photolithography-free emitter patterning approach for SHJ-IBC solar cells. To prevent laser-induced damage to the a-Si:H/c-Si heterocontact, an a-Si:H laser-absorbing layer and a dielectric mask are deposited on top of the a-Si:H/c-Si. Laser ablation only removes the top a-Si:H layer, reducing laser damage to the bottom a-Si:H/c-Si heterocontact under the dielectric mask. This dielectric mask is a distributed Bragg reflector (DBR), resulting in a high reflectance of 80% at the laser wavelength and thus providing additional protection to the a-Si:H/c-Si heterocontact. Using such simple a-Si:H patterning method, a proof-of concept 4-cm 2 SHJ-IBC solar cell with an efficiency of up to 22.5 % is achieved.

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Section: Process Flow Of Shj-ibc Solar Cellmentioning

confidence: 58%

Section: Process Flow Of Shj-ibc Solar Cellmentioning

confidence: 93%

Simple emitter patterning of silicon heterojunction interdigitated back-contact solar cells using damage-free laser ablation

Bearda

Filipič

et al. 2018

Solar Energy Materials and Solar Cells

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“…Another popular “litho‐free” alternative to patterning, which is contact‐less and also drastically reduces the number wet chemical steps, is laser ablation‐assisted patterning . In this approach, the pattern is often directly structured onto a sacrificial mask layer on top of the a‐Si:H stack to be patterned.…”

Section: Introductionmentioning

confidence: 99%

“…14 Another popular "litho-free" alternative to patterning, which is contact-less and also drastically reduces the number wet chemical steps, is laser ablation-assisted patterning. [15][16][17][18][19][20] In this approach, the pattern is often directly structured onto a sacrificial mask layer on top of the a-Si:H stack to be patterned. While there is a risk of laser-induced thermal damage to the crystalline silicon and the heterocontact in the laser-ablated areas, 19,20 significant strides have been made recently in tackling this issue.…”

Section: Introductionmentioning

confidence: 99%

A novel silicon heterojunction IBC process flow using partial etching of doped a‐Si:H to switch from hole contact to electron contact in situ with efficiencies close to 23%

Radhakrishnan

Uddin

et al. 2019

Progress in Photovoltaics

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We present a novel process sequence to simplify the rear‐side patterning of the silicon heterojunction interdigitated back contact (HJ IBC) cells. In this approach, interdigitated strips of a‐Si:H (i/p+) hole contact and a‐Si:H (i/n+) electron contact are achieved by partially etching a blanket a‐Si:H (i/p+) stack through an SiOx hard mask to remove only the p+ a‐Si:H layer and replace it with an n+ a‐Si:H layer, thereby switching from a hole contact to an electron contact in situ, without having to remove the entire passivation. This eliminates the ex situ wet clean after dry etching and also prevents re‐exposure of the crystalline silicon surface during rear‐side processing. Using a well‐controlled process, high‐quality passivation is maintained throughout the rear‐side process sequence leading to high open‐circuit voltages (VOC). A slightly higher contact resistance at the electron contact leads to a slightly higher fill factor (FF) loss due to series resistance for cells from the partial etch route, but the FF loss due to J02‐type recombination is lower, compared with reference cells. As a result, the best cell from the partial etch route has an efficiency of 22.9% and a VOC of 729 mV, nearly identical to the best reference cell, demonstrating that the developed partial etch process can be successfully implemented to achieve cell performance comparable with reference, but with a simpler, cheaper, and faster process sequence.

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“…Additionally, the use of laser ablation for SHJ-IBC patterning is being investigated by various research groups. [10][11][12][13][14] Figure 1 shows a new process flow that uses a novel laser concept referred to here as "compensation lasering".…”

Section: Introductionmentioning

confidence: 99%

Laser-induced BSF: A new approach to simplify IBC-SHJ solar cell fabrication

Vasudevan¹,

Harrison²,

d'Alonzo³

et al. 2018

AIP Conference Proceedings

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Abstract. Silicon heterojunction (SHJ) interdigitated back-contacted (IBC) solar cells currently hold the world record for conversion efficiency of silicon based, single junction solar cells. In order to use this technology for industrial applications, cost-effective strategies for amorphous silicon (a-Si:H) patterning of the back surface field (BSF) and emitter have to be developed. We propose a process flow that eliminates the need to align a-Si:H deposition steps. This is accomplished by the use of a low power, ultraviolet laser to transform an i-n-i-p a-Si:H layer stack into a fully working BSF. This process is referred to here as compensation lasering. In this manuscript, we first show a proof of concept of the compensation laser process using front and rear contacted SHJ solar cells. We then use Raman and SIMS characterization to show that the laser affects boron concentration to form a working BSF. Finally, we present precursors of a SHJ-IBC. Implied VOC values of 732 mV have been achieved showing the potential of this technique as an SHJ-IBC process.

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Laser Assisted Patterning of a-Si:H: Detailed Investigation of Laser Damage

Cited by 5 publications

References 19 publications

Simple emitter patterning of silicon heterojunction interdigitated back-contact solar cells using damage-free laser ablation

Simple emitter patterning of silicon heterojunction interdigitated back-contact solar cells using damage-free laser ablation

A novel silicon heterojunction IBC process flow using partial etching of doped a‐Si:H to switch from hole contact to electron contact in situ with efficiencies close to 23%

Laser-induced BSF: A new approach to simplify IBC-SHJ solar cell fabrication

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