Intraband spectroscopy of GaSe nanoparticles and InSe/GaSe nanoparticle heterojunctions

The spectroscopic and dynamical characteristics of electron and hole intraband transitions in several sizes of GaSe nanoparticles have been studied using polarized femtosecond transient absorption spectroscopy. Assignments of the observed absorptions are made in terms of the known GaSe band structure and a model in which the electron and hole states are described by particle-in-a-cylinder states. The results indicate that the transient absorption spectrum is due to a size-independent, z-polarized hole intraband transition, and in the smaller particles, an x,y-polarized electron transition. In InSe/GaSe mixed aggregates, direct electron transfer from InSe to GaSe nanoparticles occurs upon photoexcitation of a charge transfer band. An exciton on GaSe nanoparticles can undergo diffusion and charge separation the an InSe/GaSe heterojunction.