Process control

In order to increase the efficiency of a solar cell and achieve a higher process yield, NEXT ENERGY scientists are attempting to analyse and control the entire solar cell production sequence using both in-situ process control (during the process) and in-line process control (after the process). In the case of in-line process control, the research teams develop procedures and measurement specifications that can be used to detect large-area electrical and optical information from layers and layer packages on glass or flexible substrates. Rapid localisation of errors in the process chain of solar cell production can significantly increase the yield of production. In addition, a control loop was developed together with the company FAP GmbH, which makes it possible to optically monitor the process parameters during chemical vapour deposition (PECVD) and to adjust the deposition parameters instantaneously.

Simulation

In order to uncover existing optimisation potential in the solar cell structure and subsequently implement it in experiments, NEXT ENERGY analyses loss mechanisms in electrical and optical simulations. The scientists use the TCAD programme from Synopsys for this. "We have developed a model with which both the optical light coupling into the thin-film solar cell and the electrical transport of the charge carriers can be visualised in several dimensions," explains von Maydell. "These simulations can be used to detect optimisation potential in single, tandem or triple solar cells." Examples include the simulation of effective light-trapping structures, functional intermediate layers and new
absorber materials.

Flexible substrates

NEXT ENERGY is researching cost-effective solutions for solar cell modules based on flexible materials. Research activities in this area are currently focussed on new, more efficient solar cell architectures on metal or plastic foils with innovative light coupling concepts. In addition, new module interconnection concepts are being trialled with the help of ultrashort pulse lasers. Karsten von Maydell sees very practical application possibilities for this field of research: "By using flexible substrates such as metal or plastic foils, we have the opportunity to produce extremely lightweight solar modules. They are suitable for use on roofs, for example, which can only withstand low loads. Production costs could also be reduced in the roll-to-roll process."