Photovoltaic properties of double layer devices consisting of titanium dioxide and porphyrin dispersed hole transporting material layer

The photovoltaic effect in the double layer device consisting of titanium dioxide (TiO 2) and tetraphenyl-porphirin (TPP) blended with hole transporting material (HTM), denoted as ITO/TiO 2/TPP+HTM/Au, has been investigated in this study. Short circuit photocurrent increases drastically by the usage of double-layered structure and fluorene based monomeric material as HTM. Photovoltaic properties are improved considerably using dopants and dyes with higher ionization potential energy than that of HTM. Furthermore, it was proposed that the quantum efficiency of the photovoltaic device is improved effectively by the treatment of ionic space charge polarization (poling) when supporting electrolyte was doped into organic layers. The enhancement of photocurrent in double layer device is explained in terms of the increase of electric field at the TiO 2/organic layer interface due to the accumulation of ionic space charges.