Study on the use of TiO[sub 2] passivation layer to reduce recombination losses in dye sensitized solar cells

Abstract

A lot of research on various aspects of dye solar cells (DSC) has been carried out in order to improve efficiency. This paper analyzes the utilization of TiO2 passivation layers of different thicknesses by improving the electron transport properties. Four different thicknesses of passivation layers namely 10, 20, 50 and 100 nm were deposited onto the working electrode using r.f sputtering. The electrodes were assembled into TiO2 based DSC with active area of 1 cm2. The solar performance was investigated using 100 mW/cm2 of AM 1.5 simulated sunlight from solar simulator. The kinetics of the solar cells was investigated using Electrochemical Impedance Spectroscopy (EIS) measurement and the spectral response was measured using Incident Photon to Electron Conversion (IPCE) measurement system. The highest efficiency was found for DSC with 20 nm passivation layer. DSCs with the passivation layer have open circuit voltage, VOC increased by 57 mV, their current density, JSC increased by 0.774 mA cm−2 compared to the one without the passivation layer. The quantum efficiency of the 20 nm passivation layer is the highest, peaking at the wavelength of 534 nm, resulting in the highest performance. All DSCs with the passivation layer recorded higher ratio of RBR/RT where RT is the diffusion resistance of the TiO2 particles in the mesoscopic layer and RBR is the recombination resistance of the electron to the electrolyte. This implies that the recombination of the electrolyte I−3/3I− couple at the substrate/electrolyte interface has been effectively reduced resulting in an enhanced efficiency.