New developments in the thin film solar market continue the trend towards solar modules with higher energy conversion while at the same time, reducing significantly manufacturing costs. Especially thin film technologies based on Cadmiumtellurid (CdTe) or Cu(In,Ga)(S,Se)2 (CIGS) seem to be suited to improve the energy conversion and hence, take over larger market shares. With this work, we present our latest achievements towards a CIGS all laser scribing process with the emphasis on structuring the absorber layer and its implications to the production. While P1 laser scribing through the substrate is already implemented in production today a variety of different approaches, like lift-off, ablation, or remelting are possible for the P2 process where commonly a mechanical process is state of the art. One challenge which the P2 and P3 processes face is the layer side processing. Therefore a thorough investigation has been conducted including different laser wavelengths (355 nm to 1550 nm), pulse durations (10 ps to 100 ns), and beam shaping to find the best possible solution for each scribing process. Optimization took place utilizing not only resistance measurement and optical microscopy but also LSM, REM, EDX, EL, and Lock-In Thermography. Combining the best results of each scribing process and using a high speed, high accuracy motion system a functional lab size module has been produced with a reduced dead zone of below 200 m. In an outlook, a way is presented on how to take the lab results into a productive system and place it in a manufacturing environment.
Recent developments in Cu(In,Ga)Se2 (CIGS) thin film photovoltaics enabled the manufacturers to produce highly
efficient solar modules. Nevertheless, the production process still lacks a competitive process for module patterning.
Today, the industry standard for the serial interconnection of cells is still based on mechanical scribing for the P2 and
P3 process. A reduction of the non-productive "dead zone" between the P1 and P3 scribes is crucial for further
increasing module efficiency. Compact and affordable picosecond pulsed laser sources are promising tools towards all-laser
scribing of CIGS solar modules. We conducted an extensive parameter study comprising picosecond laser sources
from 355 to 1064 nm wavelength and 10 to 50 ps pulse duration. Scribing results were analyzed by laser scanning
microscope, scanning electron microscope and energy dispersive X-ray spectroscopy. We developed stable and reliable
processes for the P1, P2 and P3 scribe. The best parameter sets were then used for the production of functional mini-modules.
For comparison, the same was done for a selection of nanosecond pulsed lasers. Standardized analysis of the
modules has shown superior electrical performance of the interconnections and confirmed the feasibility of a dead zone
width of less than 200 ìm on an entire mini module.
The solar photovoltaic market is continuously growing utilizing boths crystalline silicon (c-Si) as well as thin film
technologies. This growth is directly dependant on the manufacturing costs for solar cells. Factors for cost reduction are
innovative ideas for an optimization of precision and throughput. Lasers are excellent tools to provide highly efficient
processes with impressive accuracy. They need to be used in combination with fast and precise motion systems for a
maximum gain in the manufacturing process, yielding best cost of ownership.
In this article such an innovative solution is presented for laser scribing in thin film Si modules. A combination of a new
glass substrate holding system combined with a fast and precise motion system is the foundation for a cost effective
scribing machine. In addition, the advantages of fiber lasers in beam delivery and beam quality guarantee not only
shorter setup and down times but also high resolution and reproducibility for the scribing processes P1, P2 and P3. The
precision of the whole system allows to reduce the dead zone to a minimum and therefore to improve the efficiency of
High Power Laser Diode Arrays developed and produced at SCD-SemiConductor Devices support a number of
advanced defence and space programs. High efficiency and unsurpassed reliability at high operating temperatures are
mandatory features for those applications. We report lifetime results of high power bar stacks, operating in QCW mode
that rely on a field-proven design comprising Al-free wafer material technology and hard soldering robust packaging. A
variety of packaging platforms have been implemented and tested at very harsh environmental conditions.
Results include a long operational lifetime study totaling 20 billion pulses monitored in the course of several years for
808 nm QCW bar stacks.. Additionally, we report results of demanding lifetime tests for space qualification performed
on these stacks at different levels of current load in a unique combination with operational temperature cycles in the
range of -10 ÷60 °C.
Novel solutions for highly reliable water cooled devices designed for operation in long pulses at different levels of PRF,
are also discussed. The cooling efficiency of microchannel coolers is preserved while reliability is improved.
Space missions are probably the most demanding environment for laser diodes. A comprehensive study on the reliability
of commercially available laser diodes arrays (LDA), with the objective of bar stacks for ESA's BepiColombo Laser
Altimeter mission to the planet Mercury was performed. We report the best results of lifetime tests performed on SCD
808 nm QCW stacks at different levels of current load in a unique combination with operational temperature cycles in
the range of -10°C to 60 °C. Based on a field-proven design that includes Al-free wafer material and a robust packaging
solution, these arrays exhibit long operational lifetime of up to 20 billion pulses monitored in the course of several years.
Zero failures and stable performance of these QCW arrays were demonstrated in severe environmental conditions
reflecting both, military and space applications. In order to achieve maximum device efficiency at different operational
conditions of the base temperature and current, an optimum combination of the wafer structure and bar design is
required. We demonstrate different types of QCW stacks delivering peak power of up to 1 kW with a usable range of
50-55% wall plug efficiency at base temperatures up to 60 °C.