Search

The crystallization by laser of amorphous or microcrystalline silicon films allows to obtain thin, high-quality, polycrystalline Si films, being a very promising method for diminishing costs in the microelectronic and solar cells sectors. During a laser crystallization process, light is partially absorbed in the amorphous silicon film, heating the sample and, if the temperature rises high enough, causing the reorganization of the film structure into a crys- talline one. In this work we show both experimental results on the crystallization of non-hydrogenated silicon thin-films performed by a continuous wave infrared laser are included, as well as a study of the process with a simple finite elements (FEM) numerical model based in the dimensional non-linear heat transfer equation with a steady heat source.

Laser crystallization of amorphous or microcrystalline silicon films to obtain high-quality polycrystalline films is one of the most promising methods for diminishing costs in the microelectronic and solar cells sectors. During a laser crystallization process light is partially absorbed by the amorphous silicon, heating the sample and, if the temperature rises high enough, causing the reorganization of the film structure into a crystalline one. In this work we show results on the crystallization of non-hydrogenated silicon thin-films by a continuous wave infrared laser, as well as a study of the process with a simple finite elements method (FEM) numerical model based in the dimensional non-linear heat transfer equation with a steady heat source.

Front metallization is an expensive, fundamental step in the fabrication of solar cells. It comprises different processes including the printing of fingers and busbars and several thermal treatments in order to cure and sinter the printed material. These two steps have been replaced by laser direct writing techniques, what allows printing fully personalized metallization designs, with high throughput velocities and a lower thermal budget for the solar cell structure.

Front metallization is an expensive, fundamental step in the fabrication of solar cells. Laser additive direct writing techniques, such as Laser Induced Forward Transfer (LIFT), can be used for printing optimized metallization patterns or free form personalized designs with applications in building integrated photovoltaics. In this work, metallic fingers and busbars have been printed onto different rigid and flexible photovoltaic materials using commercial, high viscosity, micron-sized particles, silver-based pastes. Printed lines show very large aspect ratios, low electrical resistivity and good adherence to the substrate. Functional test cells have been metallized from unfinished CIGS flexible solar cells.

In this work, the fabrication of microchannels by direct laser-writing over soda-lime glass with lasers in the nano, pico and femtosecond regimes is presented. Microchannels are the basic structure of the majority of the microfluidic devices. For the manufacturing of these chips, several materials are employed but soda-lime glass outstands among others due to its robustness and chemical resistance [1]. When using soda-lime glass, laser direct-writing is a suitable fabrication technique due to the accuracy and versatility that laser presents [2]. Physical phenomena involved in the ablation of glass in the IR range process depend on the laser pulse duration and, consequently, the morphology of the obtained structures in each case is different. For the fabrication of the channels, three different lasers were employed: a Rofin Nd:YVO4 Q-switched laser with fundamental wavelength of 1064 nm and 20 ns pulse duration, a Lumera Super Rapid-HE (Nd:YVO4) with pulse duration of 12 ps and 1064 nm wavelength and in the femtosecond regime, an amplified Ti:Sapphire laser system (Spectra Physics, Spitfire) with a pulse duration of 100 fs and 800 nm. Microchannels with similar dimensions were achieved in the three cases, with diameter around 20 μm and depth of 10 μm. The morphological properties of the ablation channels fabricated by the three approaches were analyzed in detail with SEM and 3D confocal microscopy.

The treatment of surfaces by physical or chemical methods is a very usual way to change their original properties. Although the most common use of a surface functionalization is for tribology aims, modifications of the topography that leads to changes in the surface roughness, its hydrophilicity or hydrophobicity, its light scattering behavior, biocompatibility or even aesthetic changes are possible. In this field, laser sources have proven to be a most versatile and useful tool, being a clean and fast way to achieve any of those objectives. In this work we show the results of functionalization by laser texturing of four different materials.