Doping and interfacial modification of the P3HT/ZnO photovoltaic interface: Insights from density functional theory

•PBE0 identified as the most accurate functional to model the P3HT/ZnO solar cell.•Sr-doping has a negligible impact on P3HT/ZnO adhesion while PCBA weakens adhesion.•PCBA decreases interfacial dipole to increase band offsets.•Sr decreases interfacial dipole but changes ZnO workfunction to decrease band offsets. In this work, we examine how the properties of the poly-3-hexylthiophene(P3HT)/ZnO solar cell are affected by interfacial modification with phenyl-C61-butyric acid (PCBA) and doping with Sr. Using density functional theory calculations on ideal models of the P3HT/ZnO(101¯0) interface, we characterize the equilibrium structures of the pure and modified interfaces, evaluate their ideal work of separation, and examine the energy level alignments and electronic structure. We find that doping with Sr and introducing PCBA have little impact on interfacial distances and do not strengthen interfacial adhesion. Rather, the individual and cumulative impacts of Sr-doping and PCBA are observed in changes to the energy level alignments, including the open circuit voltage and the energy offset that drives exciton separation. Sr dopants and PCBA cause these energetic shifts through differing effects on the electrostatic potential offset and interfacial dipole moments. [Display omitted]