1. Why Inverted Small Molecule Solar Cells Outperform Their Noninverted Counterparts
- Author
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Johannes B. Zimmermann, Christian Krekeler, Annemarie Pucci, Anne Katrin Kast, Tobias Glaser, Felix Schell, Wolfgang Kowalsky, Rasmus R. Schröder, Michael Scherer, Robert Lovrincic, and Diana Nanova
- Subjects
Fullerene ,Materials science ,Organic solar cell ,Electron energy loss spectroscopy ,Nanotechnology ,Heterojunction ,Substrate (electronics) ,Condensed Matter Physics ,Small molecule ,Electronic, Optical and Magnetic Materials ,Biomaterials ,Chemical physics ,Electrochemistry ,Molecule ,Deposition (law) - Abstract
It is shown that the effect of substrate heating on the photo conversion efficiency in vacuum-deposited small molecule organic solar cells is closely related to the improved free charge generation in ordered C60 regions. The formation of these ordered regions strongly depends on the deposition sequence in the device and differs therefore between inverted and noninverted cells. Substrate-induced local fullerene ordering is found in small molecule:C60 bulk heterojunctions (BHJs) deposited on pristine C60 at elevated temperatures. This does not occur for BHJs deposited under identical conditions on pristine donor molecule layers, despite similar degrees of phase separation in both cases. These findings point to a hitherto unidentified advantage of inverted over noninverted solar cells that manifests itself in a higher charge separation efficiency.
- Published
- 2015
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