Conductivity and Photoconductivity of a p-type Organic Semiconductor under Ultra-Strong Coupling

The conductivity and photoconductivity of the p-type semiconductor rr-P3HT was studied under light-matter strong coupling. The vacuum Rabi splitting with surface plasmon modes is ca. 1.2 eV corresponding to 54% of the transition energy. In this ultra-strong coupling regime, the conductivity is enhanced even for such p-type semiconductor demonstrating that ultra-strong coupling can modify the transport properties of the valence band. This effect is most easily explained by the finite photonic content of the polariton ground state under such extreme coupling conditions. Furthermore, the photoconductivity of rr-P3HT is also enhanced and show broadened spectral responses due to the formation of the hybrid polaritonic states. This is the first example of enhanced conductivity and photoconductivity for a p-type semiconductor under strong coupling. This illustrates yet again the potential of engineering the vacuum electromagnetic environment to improve the opto-electronic properties of materials.