Optical properties and carrier dynamics in Co-doped ZnO nanorods

8 figures.-- Supplementary information available.The controlled modification of the electronic properties of ZnO nanorods via transition metal doping is reported. A series of ZnO nanorods were synthesized by chemical bath growth with varying Co content from 0 to 20 atomic % in the growth solution. Optoelectronic behavior was probed using cathodoluminescence, time-resolved luminescence, transient absorbance spectroscopy, and the incident photon-to-current conversion efficiency (IPCE). Analysis indicates the crucial role of surface defects in determining the electronic behavior. Significantly, Co-doping extends the light absorption of the nanorods into the visible region, increases the surface defects, shortens the non-radiative lifetimes, while leaving the radiative lifetime constant. Furthermore, for 1 atomic % Co-doping the IPCE of the ZnO nanorods is enhanced. These results demonstrate that doping can controllably tune the functional electronic properties of ZnO nanorods for applications.WKM, AMB acknowledge Spanish MINEICO (ENE2016-79282-C5-1-R (AEI/FEDER, UE)), MICINN (PID2019-104272RB-C51/AEI/10.13039/501100011033), CSIC (2019AEP010) and Gobierno de Aragón (Grupo Reconocido DGA T03_20R).Peer reviewe