Electronic, Electrochemical, and Spectroelectrochemical Properties of Hybrid Materials Consisting of Carboxylic Acid Derivatives of Oligothiophene and CdSe Semiconductor Nanocrystals

Hybrids of CdSe nanocrytals (3.7 nm) with two types of terthiophenes, namely (4,4 ''-dioctyl-2,2':5',2 ''-terthiophene-3 ''-yl) acetic acid (L1) and 7-(4,4 ''-dioctyl-2,2':5',2 ''-terthiophene-3'-yl) heptanoic acid (L2), have been prepared via ligand exchange. Photoluminescence quenching studies showed that the efficiency of the ligand exchange is higher for L1 as compared to L2. A combination of electrochemical, spectroscopic, and spectroelectrochemical investigations gave access to the position of the HOMO and LUMO levels of the inorganic and organic components of the hybrids. Both types of hybrids show staggered alignment of these levels, which is appropriate for photovoltaic applications. Voltammetric oxidation of the CdSe-L2 hybrid leads to the dimerization of the capping ligands and the formation of a new composite material consisting of NCs embedded in the terthiophene dimer matrix. The organic component of this new material can be electrochemically reversibly switched between the doped (conducting) and undoped (semiconducting) states. The obtained hybrids can be blended with poly(3,3 ''-dioctyl-2,2':5',2 ''-terthiophene) (PDOTT) or regioregular poly(3-hexylthiophene) (P3HT), two well-known components of organic electronics devices.