Enhanced charge separation by oriented growth of Ta3N5-Cu2O n-p array heterojunction.

Tantalum nitride (Ta3N5) is one of the most promising photoresponsive semiconductor materials for efficient solar energy conversion, but its fast carrier recombination has hindered research progress severely. Fabricating a heterojunction structure is an effective strategy to promote the charge separation efficiency and thus enhance solar conversion efficiency. Herein, we designed a p-n heterojunction photoanode consisting of n-type Ta3N5 nanorod arrays (NRAs) that grew along the a-axis (light electron effective mass) and p-type Cu2O nanoparticles. This NRA heterojunction shortens the hole diffusion distance, transfers electrons along the a-axis effectively, and enlarges the space charge region. The heterojunction improves the charge separation efficiency of Ta3N5 NRAs significantly, and Ta3N5-Cu2O exhibits a photocurrent density of 9.19 mA cm−2 at 1.6 V vs normal hydrogen electrode (VNHE, pH = 0), an onset potential of 0.326 VNHE, and a maximum incident photon to current efficiency of 60% at 380 nm. Our results demonstrated a potential crystal oriented growth strategy of nanostructured heterojunctions for overcoming the short carrier diffusion distance and fast carrier recombination. [ABSTRACT FROM AUTHOR]