ACS Energy Letters · 2018 · 361 citations · 46 references
Natural SciencesMaterials EngineeringMaterials ScienceElectronic MaterialsSemiconductor MaterialsThin FilmsCarrier TransportPerovskite MaterialsPhotovoltaic DevicesPhotovoltaic MaterialsSolar Cell MaterialsSolar CellsElectron Transport LayersExternal Quantum EfficiencyHole TransportHole Transport LayersOpen-circuit VoltagePerovskite Solar CellsPhotoluminescenceSurface Recombination
We demonstrate open-circuit voltages exceeding 1.26 V for inverted planar CH3NH3PbI3 solar cells fabricated using a combination of lead acetate and PbCl2 precursors leading to smooth films and large grain sizes. Surface recombination is suppressed by careful optimization of the PTAA hole transport and PCBM electron transport layers. Suppression of bulk and surface recombination is verified by absolute photoluminescence measurements with external quantum efficiencies of ∼5% in complete cells. In addition, we find exceptionally long photoluminescence lifetimes in full cells and in layer stacks involving one or two contact layers. Numerical simulations reveal that these long photoluminescence lifetimes are only possible with extremely low recombination velocities at the interfaces between absorber and contact materials.
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