BAND ENGINEERING OF NANOSTRUCTURE PHOTOCATALYSTS AND SOLAR ABSORBERS VIA ALLOYING

摘要

Water-splitting and carbon dioxide (CO2) reduction via direct photocatalysis are forefront topics in clean, sustainable energy research. Silicon-based nanowires, widely exploited in photovoltaic and photoelectrochemical technologies, could potentially be good photocatalysts but requires further tuning of their electronic band characteristics via nanosizing and alloying to boost its photocatalytic performance. With these motivations, we mapped out for Si nanowires (NWs) alloyed with other group 4 elements (C, Ge, Sn), the relationship between their alloy structures and electronic band characteristics from accurate first-principles hybrid functionals, cluster expansion and Monte Carlo simulations. Moreover, focusing on Ge-Si nanowires, we showcase how via the combination of size and composition, one could design stable core-shell nanowire photocatalysts with (i) the appropriate band alignments to photocatalyse water-splitting and CO2 reduction, (ii) optimised band gaps for efficient solar conversion and (iii) enhanced charge separation to reduce electron-hole recombination rates.