Paramagnetic States in Oxygen-Doped Boron Nitride Extend Light Harvesting and Photochemistry to the Deep Visible Region

A family of boron nitride (BN)-based photocatalysts for solar fuel syntheses have recently emerged. Studies have shown that oxygen doping, leading to boron oxynitride (BNO), can extend light absorption to the visible range. However, the fundamental question surrounding the origin of enhanced light harvesting and the role of specific chemical states of oxygen in BNO photo-chemistry remains unanswered. Here, using an integrated experimental and first-principles-based computational approach, we demonstrate that paramagnetic isolated OB3 states are paramount to inducing prominent red-shifted light absorption. Conversely, we highlight the diamagnetic nature of O-B-O states, which are shown to cause undesired larger band gaps and impaired photochemistry. This study elucidates the importance of para-magnetism in BNO semiconductors and provides fundamental insight into its photophysics. The work herein paves the way for tailoring of its optoelectronic and photochemical properties for solar fuel synthesis.

Automated summary

A family of boron nitride (BN)-based photocatalysts for solar fuel syntheses have recently emerged. Studies have shown that oxygen doping, leading to boron oxynitride (BNO), can extend light absorption to the visible range. This study demonstrates the importance of paramagnetic isolated OB3 states in inducing red-shifted light absorption and highlights the detrimental effects of diamagnetic O-B-O states on photochemistry in BNO semiconductors. The findings provide fundamental insights into the photophysics of BNO and pave the way for tailoring its optoelectronic and photochemical properties for solar fuel synthesis.