Polyaniline-Si nanoparticle nanocapsules as a dual photovoltaic sensitizer

We examine the optical and structural properties of polyaniline-silicon nanoparticle capsules - A novel organic/inorganic material. The Si particles absorb UV/blue efficiently and green moderately, while polyaniline (PANI) in its green emeraldine state absorbs UV and red/IR efficiently, effectively providing absorption over a wide range of the solar spectrum. The capsules are produced by miniemulsion of aniline monomers in the presence of Si nanoparticles. Thin films of the capsules were formed on a variety of substrates. We use high resolution transmission electron microscopy (HTEM) and scanning electron microscopy (SEM) to record the structural properties. We also monitor the optical properties of the Si core and the PANI shell using fluorescence microscopy under UV and visible irradiation. Upon on-off cycles of UV irradiation and visible light, the red core switches reversibly between bright and dark states while PANI switches reversibly between emeraldine green and pernigraniline violet states. The results are analyzed in terms of excitonic excitation, charge separation, and transport between the core and the shell, which is useful for photovoltaic applications.