Photoinduced energy shift in quantum-dot-sensitized TiO2: A first-principles analysis

We investigate the photoinduced dipole (PID) phenomenon, which holds enormous potential for the optimization of quantum dot-sensitized solar cells (QDSSCs), by means of first-principles electronic structure calculations. We demonstrate that the sensitization of the TiO2 substrate with core/shell QDs produces almost no changes in the ground state but decisively improves the performance upon photoexcitation. In particular, the maximum attainable VOC is predicted to increase by ~25 meV due to two additive effects: (i) the displacement of the photoexcited hole away from the TiO2 surface and (ii) the interfacial electrostatic interaction established between the TiO2-injected electrons and the holes residing in the QD core. We believe that this work, explaining the mechanisms by which PID cells deliver better efficiencies, paves the way for the design of new QDSSCs with improved efficiencies.