Efficiency enhancement of solar cell by down-conversion effect of Eu3+ doped LiGdF4

The down-conversion effect of Eu3+-doped LiGdF4 (LGF) for increasing the cell efficiency on dye-sensitized TiO2 solar cells has been studied. The dye-sensitized solar cell (DSC) consisting of mesoporous TiO2 electrode deposited on transparent substrate, an electrolyte containing I-/I3-redox couple, and Pt counter electrode is a promising alternative to the inorganic solar cell [1]. The structure of DSC is basically a sandwich type, viz., F-doped SnO2 (FTO) glass/Ru-red dye-absorbed TiO2/iodine electrolyte/sputtered Pt/FTO glass. The cell without down converter had an open circuit potential of approximately 0.66 Volt, short-circuit photocurrent density of 1.632 mA/cm2, and fill factor of about 50 % at the excitation wavelength of 550 nm. An incident light intensity of 5.6 mW/cm2 was used from a light source. From this result, the calculated monochromatic efficiency at a wavelength of 550 nm of this cell was about 9.62 %. The incident-photon-to-current conversion efficiency (IPCE) of N3 used as a dye in this work is about 80 % at around 550 nm, and about 70 % at around 590 nm and 610 nm, which is the emission spectrum of Eu3+-doped LGF. From these results, we can expect an efficiency increase for DSC by using Eu3+-doped LGF as a down-converter in the front side of the cell.