Design, synthesis, characterization, and photovoltaic applications of conjugated polymer hybrids containing coordinatively binded semiconducting nanocrystals

Organic-inorganic hybrids containing organic conjugated polymers and inorganic semiconducting nanocrystals are fascinating optoelectronic materials which may combine the advantages of both worlds. This dissertation aims at developing rod-coil diblock copolymers with semiconducting nanoparticles coordinatively binded to the coil block. A mechanochemical process has been shown to be a viable and economical approach to prepare uncapped composition tunable semiconducting nanocrystals including CdSexS1- x, CdxZn1- xS, and CdSexTe1- x. The resulting II-IV nanocrystals are chemically homogenous with average sizes lower than ~10 nm, and show a linear lattice parameter-composition relationship. The CdSexS1- x and CdxZn1- xS series show close-to-linear relationship between the bandgap energy and the composition. The ternary CdSe0.25Te0.75, CdSe0.5Te0.5 and CdSe0.75Te0.25 nanocrystals show strong absorption in the NIR range presumably due to both optical bowing effect and Te induced crystal defects.;Colloidal CdSe nanocrystals have also been prepared by wet chemical methods with organic capping ligands. Three rod-coil diblock copolymers (DCPs) of the modified poly(3-hexylthiophene)-polystyrene (P3HT-PS) type with different phosphorus-containing functional groups for binding to inorganic nanoparticles have been designed and synthesized. Their corresponding P3HT-PS-CdSe nanocomposites were prepared by ligand-exchange with chemically prepared CdSe nanocrystals. Solid state absorption and fluorescence measurements indicate that the electronic energy states of the polymers are affected by CdSe. Solar cell devices of the three hybrids showed high open circuit voltages of 1.13~1.40 V and improved power conversion efficiencies over devices of the corresponding P3HT-PS diblock copolymers without cluster attachment. The improvement of the PCE is believed to be brought by intimate contact between the P3HT and the CdSe, which enhances the initial charge separation. The device performance is however hampered by the low nanoparticle loading.;Carbon nanoparticles (CNPs) with average sizes around 40-60 nm can also be prepared by the high energy ball milling process. The CNPs was utilized as an interfacial layer between TiO2-coated ZnO nanorod arrays and P3HT polymer. They are found to form close and intimate contacts with both TiO2 through carboxylic acid binding and P3HT polymer presumably by way of pi--pi interaction. The resulting hybrid solar cells showed the highest photocurrent ever reported among the similar type of device.