Monolithic interconnection of CIGSSe solar cells by picosecond laser structuring

Self Cite

We report on the optimization of selective picosecond laser structuring for the monolithic serial interconnection of (Cu(In,Ga)(S,Se)2) CIS thin film solar cells. We introduce a quantitative value to compare the energy efficiency of the different investigated laser processes, the specific ablation energy, which indicates the required energy to remove a certain volume of the specific material. We have examined the structuring efficiencies for induced laser ablation processes for a modification of the beam profile (elliptical and flat‐top beam shaping) and for the application of different laser wavelengths (1064 and 532 nm). Application of induced laser processes (often referred as “lift‐off”) decreases the specific ablation energy dramatically by nearly one order of magnitude. Modifications of the beam profile such as elliptical and flat‐top beam shaping are nearly halving the energy per ablated volume relative to a circular beam. The application of a laser wavelength 532 nm decreases the specific ablation energy compared with 1064 nm significantly for processes involving the CIS layer. We finally demonstrate that with a picosecond laser power of only 2 W, the molybdenum back contact (P1, glass side) and the ZnO front contact (P3, ZnO on CIS) can be structured with a process speed of up to 4 m/s. About 2 µm thick CIS layer (P2) is structured by standard direct laser ablation at higher energy densities with 200 mm/s. Copyright © 2012 John Wiley & Sons, Ltd.

Section: Resultssupporting

confidence: 80%

Optimization of picosecond laser structuring for the monolithic serial interconnection of CIS solar cells

Heise

Heiß²,

Hellwig

et al. 2012

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“…Figure shows as an example a graph to determine the ablation threshold of CIS (P2). Graphs for P1 and P3 have been published elsewhere .…”

Section: Resultsmentioning

confidence: 99%

Demonstration of the monolithic interconnection on CIS solar cells by picosecond laser structuring on 30 by 30 cm² modules

Heise

Börner

Dickmann

et al. 2014

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In this paper, we present the selective structuring of all three patterns (P1, P2 and P3) of a monolithic interconnection of CIS (Cu(In,Ga)(S,Se) 2 ) thin film solar cells by picosecond laser pulses at a wavelength of 1064 nm. We show results for single pulse ablation threshold values and line scribing of molybdenum films on glass (P1), CIS on molybdenum (P2) and zinc oxide on CIS (P3). The purposes of these processes are the p-type isolation (P1), cell interconnect (P2) and n-type isolation (P3), which are required for complete cell architecture. The half micron thick molybdenum back electrode can be structured with a process speed of more than 15 m/s at about 15 W average power without detectable residues and damage by direct induced laser ablation from the back side (P1). The CIS layer can be structured selectively down to the molybdenum at process speeds up to 1 m/s at about 15 W average power, due to the precision of direct laser ablation in the ultrashort pulse regime (P2). The ZnO front electrode layer is separated by clean trenches with straight side walls at process speeds of up to 15 m/s at about 10 W average power, as a result of indirect induced laser ablation (P3). A validation of functionality of all processes is demonstrated on CIS solar cell modules (30 × 30 cm 2 ). By replacing one state-of-the-art process by a picosecond laser process at a time, solar efficiencies could be increased for P1 and P2 and stayed on a similar level for P3. After an optimization of the patterning processes in the R&D pilot line of AVANCIS, we achieved a new record efficiency for an all-laser-patterned CIS solar module: 14.7% as best value for the aperture area efficiency of a 30 × 30 cm 2 sized CIS module was reached. Copyright

“…It is known that the P1 structuring through transparent substrate is an efficient and fast process . This process can be called “lift‐off” or “direct induced ablation” . The requirement for P1 is the galvanic separation not only of Mo back contacts but also of devices after module completion.…”

Section: Resultsmentioning

confidence: 99%

“…In Table , process parameters are indicated, which remove the CdS/ZnO and a small portion of CIGS at the front surface as shown in Figure (b). This process can be called “lift‐off” also or “indirect induced ablation” . Because this process is induced by selective absorption of the pulse energy in CIGS through ZnO and CdS, certain damage by heat could occur .…”

Section: Resultsmentioning

confidence: 99%

“…The mechanical structuring has been widely adapted, and high efficiencies were reported . However, utilization of laser scribing for all patterning with the structure as in Figure (a) has resulted in inadequate performances . Recently, with picosecond laser, Figure (b) type structuring, in which highly conductive TCO layer was removed leaving CIGS layer, was realized, and an efficiency of 14.7% was reported , although the efficiency is not as high as that with mechanical structuring.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

A monolithically integrated high‐efficiency Cu(In,Ga)Se₂ mini‐module structured solely by laser

Nishiwaki

Burn

Buecheler

et al. 2015

Monolithically integrated Cu(In,Ga)Se2 mini‐modules were fabricated in order to reduce the width of patterning related dead area. The Cu(In,Ga)Se2 layers were prepared on soda‐lime glasses using the multistage process at low substrate temperature below 500 °C. A picosecond laser with a wavelength of 532 nm was used for all of the structuring processes (P1, P2, and P3) for the monolithic integration. A “lift‐off” type structuring was applied for P1 and P3, and an “ablation” type was for P2. The laser structuring was optimized to be minimizing the dead area width, and the width of about 70 µm was successfully achieved. A mini‐module, in which the optimized structuring processes were applied for the integration, demonstrated a certified efficiency of 16.6%. Copyright © 2015 John Wiley & Sons, Ltd.