Photogeneration and photovoltaic effect in poly(N-vinylcarbazole):TiO2 bulk-heterojunction elaborated by hydrolysis-condensation reactions of TiO2 precursors

TiO2:poly(N-vinylcarbazole) (PVK) bulk-heterojunctions (BHJ) have been elaborated from a blend of a TiO2 precursor with the polymer in solution. The TiO2 precursor is hydrolyzed with the surrounding air humidity in thin film. Titanium isopropoxide [Ti(iOPr)4] and Tetrakis (9H-carbazole-9-yl-ethyl-oxy) titanium [Ti(OeCarb)4] were used as TiO2 precursor. Photogeneration quantum yield in BHJ of TiO2:PVK were determined by the surface potential decay (SPD) technique. Photovoltaic effect was studied in ITO/PEDOT:PSS/TiO2:PVK/Al structures. It was found that the photovoltaic performance is strongly dependent on the homogeneity of the blends. The improved dispersion of the TiO2 phase obtained with the precursor bearing a carbazole group allows efficient electron transport and fill factor enhancement of the photovoltaic devices.