Enhanced power conversion efficiency of dye-sensitized solar cells with Li2SiO3-modified photoelectrode

Abstract

The effects of lithium silicate (LS) as a surface modifier on the performance of dye-sensitized solar cells (DSSCs) were studied. LS-modified TiO<inf>2</inf> electrodes (LS-TiO<inf>2</inf>/FTO) prepared by a soaking process were applied to the photoelectrodes of DSSCs. The reference device without any modification showed performance of 0.68 V of open-circuit voltage (V<inf>oc</inf>), 21.40 mA/cm2 of short-circuit current (J<inf>sc</inf>), and 63.21% of fill factor (FF), which led to a power conversion efficiency (PCE) of 9.20%, whereas for the device with the LS-TiO<inf>2</inf>/FTO electrode, the PCE was increased to 10.58% (V<inf>oc</inf> = 0.79 V, J<inf>sc</inf> = 20.22 mA/cm2, and FF = 66.21%). By monitoring the changes in dark current-voltage characteristics, normalized IPCE spectra, and electrochemical impedance spectra, it was revealed that the LS modification induced the formation of a surface dipole on the TiO<inf>2</inf> photoelectrode, leading to the conduction band edge shift of TiO<inf>2</inf> toward a negative direction, and thus to an enhancement in V<inf>oc</inf> and a decrease in J<inf>sc</inf>. © 2015 Elsevier B.V. All rights reserved.