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

Abstract

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

Effects of Laser‐Scribed Mo Groove Shape on Highly Efficient Zn(O,S)‐Based Cu(In,Ga)Se2 Solar Modules

“…By adjusting the laser intensity, beam shape, and incidence direction (Figure d), various groove shapes are obtained, with the corresponding results shown in Figure g. Similar to a previous study, as shown in Figure g1 and g2, a Mo groove with sharp vertical edge can be obtained with configurations of L1 and L2, by an incident scribing laser beam from either the Mo side or the glass side. As reported in the literature, for P2, grooves with a gradual slope instead of an abrupt edge are always preferred to form continuous TCO films to reduce the series resistance .…”

“…Seemingly, P1 is a simple and easy process in the module fabrication process and only requires removal of the back‐contact film (e.g., Mo thin film in CIGS‐based solar devices), where the quality is always assessed by the microscopic images . As a consequence, there is limited information regarding the shape of the P1 groove edge in the region between Mo and glass substrate and its influence on the final CIGS modules.…”

Printed interconnects for photovoltaic modules

“…Here, transitioning from ns-pulsed lasers to ps-pulsed lasers for ablation provides advantages, enabling both narrower and more uniform scribing due to reduced thermal effects [1][2][3][4][5]. This also reduces unintended deposition of ablated materials on scribe sidewalls, which unmitigated create shunting pathways [4,5]. Other authors report IC width down to 250 µm using a combination of pulsed-laser and optimized mechanical scribing [6].…”

A Deep Insight into the Electronic Properties of CIGS Modules with Monolithic Interconnects Based on 2D Simulations with TCAD

“…Mechanical patterning of P2 and P3 is known to create fewer smooth trenches compared to laser ablation [20]. However, scribing P2 and P3 by nanosecond laser ablation is not recommended, as it might also damage the back contact [21]. According to reference [21], structuring of P2 and P3 scribes can be performed with picosecond laser ablation.…”