Comparison of titania and europium tellurium oxide semiconductors in the use of dye-sensitised solar cells

Abstract

Energy demand is increasing rapidly every year due to the technological growth occurring across the globe. Photovoltaics are among the preferred methods to answer this ever increasing energy demand. Although photovoltaics are so highly preferred, there are still numerous drawbacks needed to be solved before it can be accepted as the main solution for energy production. Even if photovoltaics is not directly contributing to pollution by only harvesting solar energy, it still is a costly production process, encompassing expensive construction materials, and low efficiencies as well as costly energy storage methods. Dye-sensitised solar cells are one of the photovoltaic technologies studied due to their cheap production process in comparison to its silicon solar cell counterpart. In this paper, characteristics of TiO2 dye-sensitised solar cells are studied and compared to europium tellurium oxide dye-sensitised solar cells (DSSCs). The reason for this comparison is to mainly compare dark current production between the two types of dye-sensitised solar cells. Promising results have been seen when using Eu(II)TeO6 as the semiconductor. TiO2 DSSCs have demonstrated a loss of max power output (Pm) of 99.6 % when illumination was halted, whereas Eu(II)TeO6 DSSCs held the Pm above 80 % and even demonstrating a Pm while utilising pure dark current that is 35 % higher than the Pm obtained during illumination. While Eu(II)TeO6 has exhibited this reoccurring increase in performance without illumination, it was also seen that when decreasing the particle size of Eu(II)TeO6, resulted in an increase of current produced. It has been seen that the smaller particle size Eu(II)TeO6 obtained an increase in dark current as much as double the dark current produced before being illuminated. Eu(II)TeO6 DSSCs with a particle size of 9.06 μm has been seen to be heavily affected by an increase in voltage whilst the Eu(II)TeO6 DSSCs with a particle size of 30.07 μm were less affected by the increase in bias. When continuously illuminating the TiO2 DSSCs for 5 minutes, it was seen that no Pm or efficiency could be calculated after illumination, because there was no current present the moment the voltage increased (Voc < 0.001 V) however, the Eu(II)TeO6 DSSCs were able to produce a Pm as well as exhibit cell efficiency without being illuminated All three types of DSSCs (TiO2, Eu(II)TeO6 and Eu(III)TeO6) were constructed by using identical components such as; N719 as the sensitiser, 0.5 lithium iodide and 0.05 M iodine solution in acetonitrile as the electrolyte and scotch tape used as the spacer (60 μm thick). Even though Eu(II)TeO6 exhibited a unique characteristic that is not present in TiO2, it still only produces a small fraction of current density when compared to the standard TiO2 generally used in dye-sensitised solar cells.