Part of our research focuses on the preparation and study of new organic/inorganic hybrid materials, composed of pi-conjugated polymers or oligomers and semiconductor nanocrystals. Conjugated polymers offer unique physical properties which cannot be obtained for conventional polymers. Both in their undoped (semiconducting) and doped (conducting) states, conjugated polymers can be used as components of so called 'plastic electronics'. In their neutral (undoped) state they are materials, which combine electronic properties of intrinsic semiconductors with mechanical properties and solution processibility of macromolecular systems. Moreover they frequently dissolve in the same solvents as the ones that are used to disperse colloidal nanocrystals. Thus conjugated polymers/nanocrystal composite films can relatively easily be prepared by casting from a common solvent. Although conjugated polymer/nanocrystal composites should exhibit significant advantages over both all-organic materials and inorganic semiconductors, still considerable research efforts are necessary to improve their perfromances. The main difficulty is caused by the fact that several important properties of the composite, such as charge carriers mobility, electroluminescence etc. are strongly dependent on even small changes in the polymer supramolecular structure and on the distribution of the nanocrystals within the polymer matrix, which are not easy to control. One way to probe the different charge transfer processes in hybrid blends is the use of light-induced electron paramagnetic resonance spectroscopie (EPR). 

Electronic processes possible in a P3HT:PCBM:CuInS2 ternary blend.

One of our strategies for a better morphology control consists of the formation of covalent bonds or complexing between the two constituents of the hybrid material. Parallel to this, we are exploiting pathways relying on supramolecular self-assembly. Finally, we are using the unique auto-assembly properties of poly(alkylhiophenes). Depending on the processing conditions, they can form for example fibrillar structures of high aspect ratio. Directional epitaxial solidification can lead to vertical phase segregation resulting in a lamellar structure consisting of alternating crystalline and amorphous zones. Nanocrystals can selectively be sequestered in the amorphous zones.

Further reading

Funding from the French Research Agency ANR (MYOSOTIS), from region Rhone-Alpes (research clusters Micro/Nano and Energy) and from CEA (program DSM Energy) is acknowledged.