External contacts formation for thin-film III–V solar cells exploiting inkjet printing

The development of advanced thin-film III–V solar cells requires deploying electrical contacting technology to avoid performance degradation associated with the use of standard techniques. Given the thickness of only a few micrometers of such devices, the use of standard wedge wire bonding causes mechanical damage, while manual wire bonding with silver-epoxy contacts leads to electrical losses. To address these limitations, we introduce an approach for the fabrication of external electrical connection based on Inkjet printing processes routinely deployed in printable electronics technology. The method involves a printed polymer isolation layer and e-beam deposition of Au layer connecting the front metal grid to the external contact pad. A proof-of-concept GaAs thin-film solar cell with functional contacts is demonstrated. Notably, the device exhibits good photovoltaic properties and a significant reduction in electrical losses (>7%) compared to contacts fabricated using wire bonding. The method demonstrated an open practical approach for reliable and scalable fabrication of thin-film solar cells exploiting wafer-level epitaxial lift-off processes.