Photogenerated charge carriers in semiconductor nanomaterials for solar energy conversion

Abstract

Semiconducting nanomaterials possess unique optical and electronic properties ideally suited for solar energy harvesting applications, including tuneable optical absorption due to quantum confinement effects. With above bandgap light excitation, photogenerated charge carriers (PCCs) can be collected as electricity in photovoltaic solar cells, used directly in photocatalytic redox reactions, or utilised to drive chemical reactions in photoelectrochemical (PEC) devices. Inherent electron hole recombination and charge carrier trapping usually compete with and limit the efficiency of charge separation, collection, transport, or reaction. The advantage of using semiconductor nanomaterials for solar devices is the ability to manipulate their electronic band structures and thereby alter their opto-electronic properties and functionalities. To understand the fundamental charge carrier dynamics, various time-resolved techniques that directly probe the carrier lifetime and behaviour have been employed. This review focuses on new strategies to increase the separation of charge carriers using methods such as quantum dot (QD)-sensitisation of metal oxides (MOs), elemental doping, or combined approaches for achieving synergistic effects.