Synthesis and properties of a photovoltaic cell based on polystyrene-functionalised Si nanowires filled into a poly(N-vinylcarbazole) matrix

Grafting of polystyrene (PS) from silica coating of silicon nanowires (SiNWs) has improved the dispersion of SiNWs in poly(N-vinylcarbazole) (PVK) matrix to form a bulk heterojunction (BHJ) hybrid photovoltaic (HPV) cell. First, an alkoxyamine, based on N-tert-butyl-N-(1-diethylphosphono-2,2-dimethylpropyl) nitroxide (DEPN) was covalently attached onto SiNWs through free surface silanol groups. Then, polystyrene chains with controlled molecular weights and narrow polydispersities were grown from the alkoxyamine-functionalized SiNWs surface in the presence of a “free” sacrificial styrylDEPN alkoxyamine. Both the initiator and the polystyrene chains were characterized by FTIR and 13C Solid-State NMR and quantified by TGA. The hybrid layer of SiNWs and PVK, results in cell performance improvement in respect to a reference cell based on PVK alone. A fill factor of 50% is achieved upon inclusion of PS grafted SiNWs.