Synergistic Doping of Fullerene Electron Transport Layer and Colloidal Quantum Dot Solids Enhances Solar Cell Performance

DOI: 10.1002/adma.201404411 and interface carrier density. The energetics of these interfaces must be fi nely adjusted to ensure that electrons injected into the electron acceptor are extracted prior to encountering a hole. Modifying the interface between TiO 2 and CQDs with an ultrathin atomic-alyer-deposition (ALD) ZnO buffer layer with lower surface, recombination velocity can reduce the interface recombination and improve the cell open-circuit voltage ( V oc ). To accomplish this, the interface buffer layer is required to be not only trap-free but also properly aligned with the energy levels of TiO 2 and CQDs ( Figure 1 ). [ 12 ] Unfavorable band alignment between ZnO and TiO 2 was previously found to compromise the short-circuit current ( J sc ), resulting in only minor improvements in overall power conversion effi ciency (PCE). [ 13 ]