We report measurements of a coherent coupling between surface plasmon polaritons (SPP) and quantum well excitons in a hybrid metal-semiconductor nanostructure. The hybrid structure is designed to optimize the radiative exciton-SPP interaction which is probed by low-temperature, angle-resolved, far-field reflectivity spectroscopy. As a result of the coupling, a significant shift of approximately 7 meV and an increase in broadening by approximately 4 meV of the quantum well exciton resonance are observed. The experiments are corroborated by a phenomenological coupled-oscillator model predicting coupling strengths as large as 50 meV in structures with optimized detunings between the coupled exciton and SPP resonances. Such a strong interaction can, e.g., be used to enhance the luminescence yield of semiconductor quantum structures or to amplify SPP waves.

Photovoltaic conversion was achieved from high-density p-n heterojunctions between single-wall carbon nanotubes (SWNTs) and n-type crystalline silicon produced with a simple airbrushing technique. The semitransparent SWNT network coating on n-type silicon substrate forms p-n heterojunctions and exhibits rectifying behavior. Under illumination the numerous heterojunctions formed between substrate generate electron-hole pairs, which are then split and transported through SWNTs (holes) and n-Si (electrons), respectively. The nanotubes serve as both photogeneration sites and a charge carriers collecting and transport layer. Chemical modification by thionyl chloride of the SWNT coating films was found to significantly increase the conversion efficiency by more than 50% through adjusting the Fermi level and increasing the carrier concentration and mobility. Initial tests have shown a power conversion efficiency of above 4%, proving that SOCl(2) treated-SWNT/n-Si configuration is suitable for light-harvesting at relatively low cost.

We report solar cells based on high-density p-n heterojunctions between single wall carbon nanotubes (SWCNTs) and a n-type silicon wafer. Chemical modification by thionyl chloride of the SWCNT coating films was found to significantly increase the conversion efficiency by more than 45% through adjusting the Fermi level and increasing the carrier concentration and mobility. Electron-hole pairs are optically excited in the numerous heterojunctions formed between SOCl2-treated SWCNTs thin coating and n-type silicon substrate, and then split and transported through SWCNTs (holes) and n-Si (electrons), respectively.

In situ polymerization of thiophene to poly(3-hexylthiophene) (P3HT) was carried out in the presence of different loadings of multiwall carbon nanotubes (MWNTs) (0.1-10 wt %). It was found that the nanotubes are dispersed uniformly in the polymer matrix and the polymer chains wrap around the nanotube walls. NMR analysis indicated the presence of both CH-π and π-π interaction between P3HT and MWNTs, thereby enhancing the optical, thermal, and electrical properties of the nanocomposite for certain loadings of MWNTs. With an increase in MWNT concentration the head-tail (H-T) regioregularity of the composites was found to decrease. The UV-vis spectra of the composite films show a red shift of the π-π* transition band with increasing MWNT concentration, which was attributed to the uncoiling of the P3HT chain on the MWNT surface. Additionally, the charge carrier transport phenomenon was studied for these nanocomposites. The temperature-dependent conductivity measurement revealed that the addition of MWNTs into P3HT polymer shifted the main conduction mechanism from variable-range hopping to fluctuation-assisted tunneling, and the polymer acted as a barrier in bundle-to-bundle hopping.