Improvement of near-infrared photoelectric conversion efficiency of solution-coated (C₈BTBT)(F₄TCNQ) films by adding Fe₃O₄ nanoparticles

Abstract

To realize transparent photoelectric conversion elements useful for optical wireless power-transmission systems and sensors, we investigated thin films of 2,7-dioctyl[1]benzothieno [3,2-b][1]benzothiophene and fluorinated derivatives of 7,7,8,8,-tetracyanoquinodimethane (C8BTBT)(F4TCNQ) produced by a simple solution-coating method. We found that the addition of Fe3O4 nanoparticles (NPs) to a (C8BTBT)(F4TCNQ) solution promoted crystal formation and increased the optical absorption of the film. This was because the addition of NPs formed a middle layer, and the NPs acted as starting points for the formation of crystal nuclei. Photocurrent measurements confirmed that the quantum efficiency (QE) of the film with NPs was improved by about 14-fold compared with the film without NPs. The promotion of crystal formation increased the optical absorption and significantly improved QE.