Objectives and Status
Development of industrially scalable low cost processes for the front contact grid of the tandem solar cells, with Total series resistance of electrodes (contact resistance and bulk-resistance) < 1 Ohm cm² and less than 2% of the front side shaded area by electrodes.
To employ the back-end of the line (BEOL) processes developed in WP4 on solar cells, a defined layout was successfully inkjet-printed and sintered on different samples, followed by electroplating and etching steps. Afterwards, the cells were finished by coating of front anti-reflective layers and backside metallic contacts (Figure 3).
The current density-voltage (J-V characteristic) shows that the front contacts are well functional and a working solar cell could be achieved (Figure 4).
Furthermore, Aerosol-jet printing is considered as an alternative method for front side electrodes printing (seeding layer). The primary results showed very low contact resistivity of ionic ink on GaAs (< 10 mOhm cm²).
The application of the method is fast, therefore, optimization can be performed quickly. JR works on the required modifications of aerosol-jet printing and considers this method as an alternative for inkjet-printing.