Concurrent synthetic control of dopant (nitrogen) and defect complexes to realize broadband (UV–650 nm) absorption in ZnO nanorods for superior photo-electrochemical performance

Abstract

We report a facile solution based synthesis protocol to incorporate nitrogen within zinc oxide nanorods with substantially improved visible light harvesting via broadband absorption stretching from UV to deep visible wavelengths (650 nm). We also report a peculiar visible region maximum around 470 nm. Raman and X-ray photoelectron spectroscopy confirm incorporation of nitrogen along with other complex defects such as zinc interstitials and oxygen vacancies. Our N:ZnO appears pale orange as opposed to the pale yellow reported in other works. It exhibits significantly superior photo-electrochemical performance over undoped ZnO. Notably under monochromatic green light illumination (530 nm) N:ZnO shows a photocurrent density of 3.2 μA cm⁻², whereas pristine ZnO fails to show any photo-response. The IPCE spectrum of N:ZnO follows the broadband absorption spectrum extending up to an unprecedented value of 650 nm, potentially expanding the scope for using our material in other solar energy harvesting applications.