An effective bilayer cathode buffer for highly efficient small molecule organic solar cells

Novel organic/ultrathin low work function metal bilayer cathode buffers for small molecule organic solar cells are proposed. Ultrathin low work function metal layers possess a high built-in electric field for effective carrier extraction and a high cathode reflectivity for maximum absorption in the photoactive layers. This leads to a significant increase of short circuit current density and fill factor of cells. By integrating this bilayer cathode buffer with DTDCTB:C60 small molecular heterojunction, the device exhibits a high power conversion efficiency of up to 5.28%, which is an improvement of 22% compared to a device with a traditional single organic layer buffer.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► A bilayer cathode buffer for small molecule solar cells has been demonstrated. ► Introduction of the buffer results in an increase of short circuit current density and fill factor. ► The buffer establishes a high built-in electric field for effective carrier extraction. ► The devices adopting the buffer show high power conversion efficiency of 5.28%.