In order to cut and decollate silicon for the manufacturing of solar cells and electronic components, commonly blade sawing or nanosecond-based laser processes are used. If the cut needs to be carried out with a high precision and without causing any thermal damage to the surrounding material, ultrashort pulsed laser cutting can be used to deliver a fine and small cutting kerf. The reduction of the kerf width leads to a higher yield per wafer, if single elements need to be cut out. As a result, marginal heat affected zones with minimal edge damages are attainable. Ultrashort pulsed lasers range from pico- to femtoseconds. In order to demonstrate the best pulse duration and ablation strategy for the singling of silicon wafers, the ablation threshold for pulse durations is determined using the Liu’s method. Through this method, the diameter of the ablated geometry is measured, squared and plotted against the peak fluence on a logarithmic scale. With the knowledge of the ablation threshold, various influences on cutting of silicon are compared in order to create a minimal cutting kerf with reduced heat affected zone. With decreasing pulse duration, the surface of the silicon seems to be smoother and ablation is characterized by a sharp ridge. The ablation threshold of silicon depends on the temperature, so a second laser beam for pre-heating of the silicon material is coupled coaxially with the cutting beam. This arrangement is found to improve the ablation behavior of silicon.
Rechargeable lithium-ion batteries with liquid electrolytes are the main energy source for many electronic devices that we use in our everyday lives. However, one of the main drawbacks of this energy storage technology is the use of liquid electrolyte, which can be hazardous to the user as well as the environment. Moreover, lithium-ion batteries are limited in voltage, energy density and operating temperature range. One of the most novel and promising battery technologies available to overcome the above-mentioned drawbacks is the Solid-State Lithium-Ion Battery (SSLB). This battery type can be produced without limitations to the geometry and is also bendable, which is not possible with conventional batteries1 . Additionally, SSLBs are characterized by high volumetric and gravimetric energy density and are intrinsically safe since no liquid electrolyte is used2-4. Nevertheless, the manufacturing costs of these batteries are still high. The existing production-technologies are comparable to the processes used in the semiconductor industry and single cells are produced in batches with masked-deposition at low deposition rates. In order to decrease manufacturing costs and to move towards continuous production, Roll2Roll production methods are being proposed5, 6. These methods offer the possibility of producing large quantities of substrates with deposited SSLB-layers. From this coated substrate, single cells can be cut out. For the flexible decollation of SSLB-cells from the substrate, new manufacturing technologies have to be developed since blade-cutting, punching or conventional laser-cutting processes lead to short circuiting between the layers. Here, ultra-short pulsed laser ablation and cutting allows the flexible decollation of SSLBs. Through selective ablation of individual layers, an area for the cutting kerf is prepared to ensure a shortcut-free decollation.
The breakthrough of flexible organic electronics and especially organic photovoltaics is highly dependent on cost-efficient production technologies. Roll-2-Roll processes show potential for a promising solution in terms of high throughput and low-cost production of thin film organic components. Solution based material deposition and integrated laser patterning processes offer new possibilities for versatile production lines. The use of flexible polymeric substrates brings along challenges in laser patterning which have to be overcome. One main challenge when patterning transparent conductive layers on polymeric substrates are material bulges at the edges of the ablated area. Bulges can lead to short circuits in the layer system leading to device failure. Therefore following layers have to have a sufficient thickness to cover and smooth the ridge. In order to minimize the bulging height, a study has been carried out on transparent conductive ITO layers on flexible PET substrates. Ablation results using different beam shapes, such as Gaussian beam, Top-Hat beam and Donut-shaped beam, as well as multi-pass scribing and double-pulsed ablation are compared. Furthermore, lab scale methods for cleaning the patterned layer and eliminating bulges are contrasted to the use of additional water based sacrificial layers in order to obtain an alternative procedure suitable for large scale Roll-2-Roll manufacturing. Besides progress in research, ongoing transfer of laser processes into a Roll-2-Roll demonstrator is illustrated. By using fixed optical elements in combination with a galvanometric scanner, scribing, variable patterning and edge deletion can be performed individually.