Siliconnanowire/poly(3-hexylthiophene) hybrids for thin film solar cells

We have developed hybrid devices based on n type silicon nanowires (SiNWs) dispersed in a p type poly(3-hexylthiophene): P3HT, polymer film. The strong photoluminescence at 860 nm exhibited by SiNWs can be assigned to the electronic confinement effect for nanowire diameters smaller than 10 nm. An optimum dissociation of the electron-hole pairs photogenerated in P3HT by a 10 wt.% concentration of SiNWs in the blend is indicated by the extinction of the P3HT photoluminescence which is however incomplete. The current/voltage characteristics under simulated sun-light shows an open circuit voltage reaching 0.5 V, a filling factor of the order of 0.35 and a short circuit of some mA/cm2 depending on the surface treatment of SiNWs. Improved results are obtained for silicon surfaces grafted with polystyrene chains leading to surface state passivation and increased dispersion of the SiNWs in the polymer layer coming from an improved compatibility between organic and derivatized inorganic phases.