High-Performance Inverted Polymer Solar Cells with Zirconium Acetylacetonate Buffer Layers.

Inverted polymer solar cells incorporating solution-processed zirconium acetylacetonate (ZrAcac) buffer layers were demonstrated. The optimal device delivered a power conversion efficiency up to 9.2%, displaying ∼20% improvement compared with the device of conventional configuration. The performance improvement by adopting ZrAcac as the cathode buffer layer is attributed to the enhanced light-harvesting, facilitated electron transport, and reduced bimolecular recombination loss. The morphology of ZrAcac buffer layer was found to be critical in achieving high performance, which was tunable through the selection of processing solvents. A flat and uniform ZrAcac film consisting of ∼20 nm nanoscale aggregates deposited from a chloroform solution was proved to be highly effective, which only requires a short light-soaking time.