Slowing hot-electron relaxation in mix-phase nanowires for hot-carrier photovoltaics

Hot carrier harvest could save 30% energy loss in solar cells. So far, however, it is still unreachable as the photoexcited hot carriers are short-lived, 1 ps, determined by a rapid relaxation process, thus invalidating any reprocessing efforts. Here, we propose and demonstrate a feasible route to reserve hot electrons for efficient collection. It is accomplished by an intentional mix of cubic zinc-blend and hexagonal wurtzite phases in III-V semiconductor nanowires. Additional energy levels are then generated above the conduction band minimum, capturing and storing hot electrons before they cool down to the band edges. We also show the superiority of core/shell nanowire (radial heterostructure) in extracting hot electrons. The strategy disclosed here may offer a unique opportunity to modulate hot carriers for efficient solar energy harvest.