Relationship between the morphology and charge transport in the hybrid system composed of conductive polymer and CdSe nanoparticles

Hybrid systems based on a bulk heterojunction of conductive polymer and semiconductor nanoparticles is one of the promising approaches for low cost and printable solar cell fabrication. However the light conversion efficiencies of these systems are quite low (2-3 percent) compared to inorganic solar cells. One limiting factor in the organic-inorganic hybrid solar cells is the comparably low charge carrier mobility which impedes efficient charge transport. Furthermore, the morphology of the active layer is difficult to control which contributes to limited light conversion efficiency as well. In the present work, composites of poly(3-hexylthiophene) and colloidally synthesized CdSe nanoparticles were prepared. The nanoparticles possess an organic ligand shell after synthesis which needs to be replaced by pyridine prior to use in solar cells. The influence of the ligand exchange on the active layer morphology was investigated here. Charge carrier mobility was investigated by OFET methods. The results were compared with a theoretical model based on the fitting of the current-voltage characteristics. Relationships between the morphology and charge transport were analyzed.