DYE-SENSITIZED SOLAR CELLS WITH TiO2 ELECTRODE MODIFIED BY La2O3, Er2O3 or AgO

Abstract

In this research, we modified TiO2 electrode of a dye-sensitized solar cell (DSSC) by adding the second metal oxide, namely lanthanum oxide (La2O3), erbium oxide (Er2O3) and silver oxide (AgO). Moreover, we also investigated the addition of light scattering layer in the electrode by employing double layered structure. TiO2-based mixed oxides were synthesized via sol-gel methods. The mixed oxide sols were then coated on a conducting transparent glass as thin film using an ultrasonic spray coater. Finally, the thin film electrode was fired 400°C for 2 h. The amount of La2O3, Er2O3 or AgO added to TiO2 was varied from 0 to 7 %wt. The photovoltaic conversion efficiency of pure TiO2 electrode was 3.51±0.20%, as measured by an IV-tester under standard condition (AM = 1.5). When La2O3 or Er2O3 was added, the amount of dye adsorbed on the electrode increased due to larger specific surface area of the electrode. As a result, the short circuit current density (Jsc) and open circuit voltage (Voc) definitely increased in both cases. The addition of La2O3 and Er2O3 raised the cell efficiency to 5.06±0.36% with 5 wt% La2O3/TiO2 and 4.37±0.30% with 3 wt% Er2O­3/TiO2. On the contrary, the power conversion efficiency was significantly lower with AgO-TiO2 electrode. Employing the double-layered structure with pure TiO2 as under-layer and 5%wt La2O3/TiO2 as over-layer enhanced the cell efficiency from 5.06±0.36% to 7.72±0.47% compared to the single-layered La2O3-TiO2 electrode. This can be attributed to light scattering effect, which increased the reflection of light back into the cell.