Interfacial Properties of Solar Energy Materials from DFT: P3HT/ZnO and CdS/Graphene

We present two projects that demonstrate how computational quantum chemistry is used to better understand materials for solar energy applications. In the first project, we use density functional theory (DFT) to examine the P3HT/ZnO solar cell and the mechanism by which interfacial modification with PCBA and doping with Sr enhances photovoltaic efficiency. We find that the enhancement in photovoltaic efficiency is not due to changes in equilibrium structures or adhesion strengths. Rather, the impacts of Sr-doping and PCBA are linked to changes to the energy level alignments. In the second project, we focus on CdS/graphene photocatalytic interfaces. Using DFT calculations, we study the interfacial properties of CdS(0001)/graphene and a CdS/graphene bilayer, and examine whether doping with B/N can strengthen interfacial adhesion. The CdS/graphene bilayer is found to exhibit high interplanar distances and low adhesion energies, characteristic of dispersion-dominated interfacial adhesion. Doping graphene does not significantly modify the strength of adhesion, but it does enable modulation of the band edge and Fermi level alignments. The CdS(0001)/graphene interface is found to be similarly adhered via dispersion interactions, but here, doping with B strengthens interfacial adhesion.