Luminescence properties of chalcopyrite AgInS2 nanocrystals: Their origin and related electronic states

► Highly luminescent AgInS2 nanocrystals with chalcopyrite structure are synthesized. ► Photoluminescence quantum yield exceeds 40%. ► Photoluminescence mechanisms are ascribed to electron-hole pair recombination with donor-acceptor pair-like mechanisms. ► Donor and acceptor states originate from the internal defects.