Printable germanium inks for flexible optoelectronics

The ability to add functionality to flexible substrates through additive approaches using electronic and optical materials for wearable or conformal applications has become increasingly important in recent years. In this paper, the development of several germanium based semiconductor inks is detailed, their printing and post-processing using photonic annealing is demonstrated, and their electro-optic performance is characterized. A range of inks were developed, namely a pristine germanium nanoparticle ink, a nickel doped germanium nanoparticle ink, and a hybrid silver nanoparticle/germanium nanoparticle ink. Aerosol jet printing was performed on both rigid substrates and a common flexible polyimide substrate (KaptonTM). Photonic sintering was used on all three printed inks to improve their optoelectronic properties and coalesce the individual particles into a continuous film. Optical and structural characterization of the printed films was performed before and after photonic sintering to investigate morphological changes in the film. Finally, the applicability of these inks in flexible optoelectronic applications was demonstrated by measuring the photo-excited conductivity changes as well as the flexibility of the printed films.