| AVS 59th Annual International Symposium and Exhibition | |
| Applied Surface Science | Thursday Sessions |
| Session AS-ThM |
| Session: | Applications of Large Cluster Ion Beams |
| Presenter: | T. Conard, IMEC, Belgium |
| Authors: | T. Conard, IMEC, Belgium A. Franquet, IMEC, Belgium E. Voroshazi, IMEC, Belgium D. Cheyns, IMEC, Belgium P. Favia, IMEC, Belgium W. Vandervorst, IMEC, Belgium |
| Correspondent: | Click to Email |
Organic material composition profiling has always been very challenging. Recently, it has been shown that using a Gas Clusters Ion Beam source (GCIB) with large Ar–clusters, organic information can be preserved while profiling. However, very little studies have been performed yet about the influence of beam parameters on the spectra/profiles obtained.We investigated systematically the influence of the sputter parameters in a dual beam TOFSIMS experiment (Bin+/Arm+) on organic solar cells composed of PCBM and P3HT. Environmental stability of organic solar cells prepared with oxide transport layers is considerably enhanced; hence the critical importance to be able to also investigate organic/inorganic interfaces with large ion clusters.
Qualitatively, it is known that the average energy per atom is an important parameter to keep organic information: For low eV/atom, no sputtering occurs and for high energy per atom, the molecular information is lost. We show for a layer of mixed P3HT:PCBM that the transition to the loss of molecular information occurs sharply at about 6eV/atom, independently of the primary cluster energy. However, we also observe a significant variation of the intensity of the molecular peaks within the energy-region where molecular information is kept. It occurs both towards the higher and the lower eV/atom limits. These are the consequence of the dual beam experiment. At the lower eV/atom limit, the molecular information is lost due to the damage induced by the analysis beam Towards the higher eV/atom limit, we observed a decrease of the intensity of the molecular PCBM peak by a factor 2 between 2.8 and 4.0 eV/atom. This is interpreted as a partial degradation of the PCBM due to the sputtering.
Composition variations within the formed layers and/or polymer degradation are important for solar-cells devices performances. For a system like PCBM:P3HT mixed layer, one may follow the sulfur intensities throughout the layer as an indirect indication of segregation. This allows, for instance to use of energy-filtered TEM to analyze de-mixing of layers. By comparing TEM and molecular profiling, we show in this study that segregation within layers and degradation of solar cells can be analyzed by dual beam TOF-SIMS.
Finally, the interfaces between the organic and inorganic layers in a solar cell are also critical to the quality of the devices. However, the optimal analysis parameters of inorganic material using cluster ion source may significantly differ from the optimal parameters for organic layers (for instance sputtering rates). We will thus focus on the determination of the best trade-off parameters for heterogeneous systems.