Investigation of monocrystalline p-type PERC cells featuring the laser enhanced contact optimization process and new LECO paste

Krassowski, Eve; Großer, Stephan; Turek, Marko; Henning, Andreas; Zhao, Hongming

doi:10.1063/5.0056380

Cited by 11 publications

(9 citation statements)

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“…Right: Schematic cross section of the final iTOPCon solar cell Also, LECO on iTOPCon seems even more beneficial compared with PERC devices where the reported efficiency gains are in the range of 0.14%-0.37%. 16,18 4 | CONTACT RESISTIVITY Differently to PERC devices, the contact formation mechanism for iTOPCon solar cells on both sides is similar; hence, both sides might be able to benefit from LECO. Therefore, iTOPCon solar cells prior and after LECO were prepared for the transition line method (TLM) 21 by cutting them into 10 mm wide stripes.…”

Section: Resultsmentioning

confidence: 99%

“…Note: The data presented in Figure 2 and publications [16][17][18] indicate no explicit impact of LECO on V oc , so the gain in V oc comes only from the reduction of the sintering temperature enabled by LECO.…”

Section: Metal-induced Recombinationmentioning

confidence: 97%

“…The patented LECO process was discovered in 2016 from Cell Engineering GmbH, Germany and was developed initially to recover underfired solar cells, 15 and until now, was applied only to passivated emitter and rear cell (PERC)-like solar cells. [16][17][18] The LECO process locally applies a highly intense laser pulse on the front side of the solar cell, which is held at constant reverse voltage of 10 V and more. The resulting local current flow of several amperes is responsible to significantly reduce the contact resistivity ρ c between semiconductor and metal electrode.…”

Section: Experimental Approachmentioning

confidence: 99%

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Laser‐enhanced contact optimization on iTOPCon solar cells

Fellmeth

Höffler

Mack

et al. 2022

Progress in Photovoltaics

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The authors present their work on laser-enhanced contact optimization (LECO) on iTOPCon solar cells. LECO improves the metal-semi-conductor contact resistivity ρ c on the boron emitter and the n-TOPCon side from an underfired (thermal budget too low) state of 2.9 and 14.1 mΩcm 2 to an enhanced state of 1.8 and 2.9 mΩcm 2 . Therefore, it enables the reduction of the optimal peak firing temperature, which leads to a decrease of metal induced recombination mainly on the boron emitter side and to minor degree on the n-TOPCon side, as shown in this work. Ultimately, LECO improves iTOPCon solar cells conversion efficiency by 0.6% abs compared with the optimal fired, untreated reference. Submitting those cells to 140 C and 2 suns equivalent irradiation for more than 4 h shows no impact on the conversion efficiency or any sign of light and elevated temperature-induced degradation (LeTID). Confirmed by ISE CalLab, LECO improved iTOPCon solar cells reach 23.8% and 24.1% conversion efficiency on industrial typical wafer formats and processes.

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Section: Resultsmentioning

confidence: 99%

Section: Metal-induced Recombinationmentioning

confidence: 97%

Section: Experimental Approachmentioning

confidence: 99%

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Laser‐enhanced contact optimization on iTOPCon solar cells

Fellmeth

Höffler

Mack

et al. 2022

Progress in Photovoltaics

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“…[ 23 ] The power conversion efficiency is taken as a measure for the overall solar cell performance. After the initial I – V measurements, the solar cells are treated with the LECO process [ 24–28 ] and I – V measured again. LECO is a relatively new process that improves underfired silver–silicon contacts to the optimum stage and is, therefore, more and more used in the PV community.…”

Section: Methodsmentioning

confidence: 99%

Short Drying Processes for Silicon Solar Cells

Ourinson

Linse

Klawitter

et al. 2022

Physica Rapid Research Ltrs

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Herein, very short drying processes for the screen‐printed electrodes of passivated emitter and rear solar cells (PERC) are successfully demonstrated. The short drying processes are conducted in an in‐line heating system with vertical‐cavity surface‐emitting lasers (VCSEL) as its heat source, being a compact alternative to the conventional heating chamber. While the heating time of the conventional industrial drying process is believed to be about 20 s (to the best of the authors’ knowledge), the VCSEL system allows a significant reduction down to 0.15 s while maintaining a similar power conversion efficiency and contact adhesion quality.

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“…Color versions of one or more figures in this article are available at https://doi.org/ allowing the contact formation even on low-doped emitters [5]. New pastes adapted for the LECO process have been reported [4], [10] exhibiting also improved open-circuit voltages as well as a small increase in short-circuit current. We present in this contribution a first microstructure analysis of the contact formation at the silver grid finger and the silicon wafer interface.…”

Section: Introductionmentioning

confidence: 99%

Microscale Contact Formation by Laser Enhanced Contact Optimization

Groser

Krassowski

Swatek

et al. 2022

IEEE J. Photovoltaics

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A technique to improve contacts of solar cells laser enhanced contact optimization (LECO) has been studied in terms of micro scale contact formation at industrial PERC solar cells. High-resolution diagnostics by focused ion beam techniques and scanning electron and transmission electron microscopy indicate the LECO-induced formation of microscopic contacts at the buried interface between the screen-printed silver finger and the silicon wafer. A large quantity of these micro contacts where found exclusively for LECO processed cells. Target preparation and threedimension cross-section investigation reveal an interdiffusion of the Ag and Si material as the underlying root cause for improved local contact resistivity. We propose a descriptive model for local ohmic contact formation maintaining surface passivation.

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Investigation of monocrystalline p-type PERC cells featuring the laser enhanced contact optimization process and new LECO paste

Cited by 11 publications

References 0 publications

Laser‐enhanced contact optimization on iTOPCon solar cells

Laser‐enhanced contact optimization on iTOPCon solar cells

Short Drying Processes for Silicon Solar Cells

Microscale Contact Formation by Laser Enhanced Contact Optimization

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