Infiltration of Polymer Through the Pores of Electrospun Nanofibers and Performance of TiO2 Nanofibers/ P3HT Photovoltaic Devices

Metal oxide semiconductor nanofibers obtained by electrospinning are excessively used in organic-inorganic photovoltaic (PV) devices due to large surface area with low production cost. Performance of these devices depends upon the thickness of the active layer and polymer infiltration through the pores of nanofibers mat, which is controlled by electrospinning time. The parameters of hybrid photovoltaic devices, fabricated by poly (3-hexylthiophene) (P3HT) and TiO2/ Di-tetrabutylammonium cis-bis(isothiocyanato)bis(2,2'- bipyridyl-4,4'-dicarboxylato)ruthenium(II) (N719) composite nanofibers was analyzed by considering infiltration of polymer through the electrospun nanofibrous network. Power conversion efficiency (PCE) was improved from 0.13% to 0.93%. Open circuit voltage and short circuit current density were also improved to 0.61V and 3.64mA/cm2 respectively. Longer electrospinning time resulted in an increased number of fiber layers, i.e. increased thickness of the active layer. This results in higher light absorption but reduced infiltration of polymer through the nanofibrous pores up to the lowest layer due to covering up by the top layers. These factors introduce defects and increased series resistance, contributing toward decrease in device efficiency.