Charge Carrier Management in Semiconductors: Modeling Charge Transport and Recombination

Long-lived charge carriers are necessary to initiate redox reactions on photocatalyst surfaces. The ideal photocatalyst should have charge carriers with fast mobility and low recombination rates, or good "charge carrier management". Being able to predict such behavior means that new materials with desired properties can be discovered. It is necessary to understand the principles of such processes further to enable rationale catalyst design and to advance the science of photocatalysis. We review theoretical approaches to model charge transport (both band and polaron transport), as well as efforts to model charge recombination. The chapter focuses on the use of ab initio electronic structure methods, but also discusses how mesoscale modeling can provide spatial and temporal details on charge transport. We also review efforts to improve charge separation and mobility in semiconductor materials through the use of novel structures, such as heterostructures or controlled doping, and how such structures can be modeled. Theory has been essential to the field of photocatalysis and will continue to drive development of materials with improved charge transport.