Fabrication of panchromatic dye-sensitized solar cells using pre-dye coated TiO₂ nanoparticles by a simple dip coating technique

An appropriate method of pre-dye coating of TiO₂ nanoparticles (NPs) and a facile approach of a dip coating technique have been adopted for the fabrication of panchromatic dye-sensitized solar cells (DSSC). A bi-layer photoanode consists of two distinct layers of TiO₂ films, which were individually sensitized with N719 and N749 dyes and then coated on a TCO substrate in a sequenced manner. The spectral response of panchromatic DSSCs has been investigated using monochromatic incident photon to current conversion efficiency (IPCE) spectroscopy. The IPCE spectrum of panchromatic DSSC revealed the absorption characteristics of each single dye cell. The broader absorption spectra were obtained up to 850 nm of near IR region and the higher quantum efficiency than those of single cells were recorded. The higher value of IPCE is correlated with the higher short circuit current density value of panchromatic cell (J_sc = 13.4 mA cm^-2). The tandem cell showed an average open circuit voltage (V_oc = 0.79 V) of the single dye cells with an overall conversion efficiency of 7.1%. Moreover, the present approach does not require any high temperature sintering process; therefore it could be suitable for the fabrication of flexible panchromatic DSSCs.