1. To combust or not to combust, that’s the question Wouter Marchal

2. Summary  Combustion synthesis: a brief introduction  Research context: MoOx layers for OPV’s  Powder combustion case study  Oxidizer/fuel ratio  Surface/volume effect  Combustion in films?  Solution processing  OPV performance  Heating rate influence  Transparancy and morphology  Conclusion  Outlook 2

3. Combustion synthesis: a brief introduction Film synthesis from chemical solution on temperature sensitive substrates ! 3 Patil, K.C. et al., Chemistry of nanocrystalline oxide materials, 2008, world scientific, Singapore

4. Research context: MoO 3 layers in OPV’s MoO 3 hole transport layers in OPV technology MoO 3 is a promising replacement for conventional PEDOT:PSS Is combustion synthesis in films possible? Can we achieve functional MoO 3 layers? Greiner, M.T., Chai, L., Lu, Z-H., Organic photovoltaics: transition metal oxides increase organic solar cell power conversion, 2012, laserfocusworld.com 4

5. Powder combustion case study 5 ESI-MS

6. Powder combustion: oxidizer fuel ratio Explanation for deviating oxidizer/fuel ratio: Hacac evaporation around 170 °C 6 [ox/fuel] = 0.5 is optimal ratio ! TGA FTIR

7. Powder combustion: surface/volume ratio 7 1 mm 63 µm TGA DSC Combustion signal fading out for small dimensions

8. Combustion in films?  Film processing  OPV performance Spin coating of combustion precursor, thermal treatment to initiate decomposition Aver V oc 0.86 Aver J sc 7.58 Aver FF0.51 Aver PCE3.35 Best PCE3.62 Best PCE up to now: 3.62 8 j-V output Jsc and FF: room for improvement

9. TG on film: close up 9 UV-O 3 soft clean of cover glass Cover glass diameter (6 mm) just fits on the spin coater chuck Cover glass with coating in TG-MS sample pan

10. Combustion in films? Heating rate influence TG-MS analysis on film Heating rate increase: More CO 2 evolution Proportionally less evaporation decomposition products (CH 2 CO + ) FTIR on film: Difference between gradual heating and hotplate treatment Hotplate treatment corresponds to high heating rate Presence of MoO x phase 10 TG-MS FTIR-ATR

11. Combustion on films? Transparency and morphology Morphology depends on precursor concentration High precursor concentration results in inhomogeneous layer formed by sudden gas release 11 0.05 M 0.1 M 0.2 M0.3 M Combustion? UV-Vis SEM

12. Conclusions  Indications for combustion in films  Promising MoO 3 hole conducting layer performance 12 Deviating Oxidizer/fuel ratio Surface/volume effect Heating rate effect