UV Filtering of Dye-Sensitized Solar Cells: The Effects of Varying the UV Cut-Off upon Cell Performance and Incident Photon-to-Electron Conversion Efficiency

Abstract

With current technology, UV filters are essential to ensure long-term dye-sensitized solar cell (DSC) stability. Blocking photons, however, will have an obvious effect on device performance and upon its incident photon-to-current conversion efficiency (IPCE). Filters have been applied to DSC devices with a range of cut-off wavelengths in order to assess how different levels of filtering affect the performance and IPCE of devices made with three different dyes, namely N719, Z907, and N749. It is shown that dyes that extend their IPCE further into the NIR region suffer lesser relative efficiency losses due to UV filtering than dyes with narrower action spectra. Furthermore, the results are encouraging to those working towards the industrialisation of DSC technology. From the results presented it can be estimated that filtering at a level intended to prevent direct band gap excitation of the TiO2semiconductor should cause a relative drop in cell efficiency of no more than 10% in forward illuminated devices and no more than 2% in reverse illuminated devices.

Stability of templated and nanoparticles dye-sensitized solar cells: photovoltaic and electrochemical investigation of degradation mechanisms at the photoelectrode interface

“…In the case of liquid DSSCs, I 3 − from the electrolyte was identified as the most affected by UV exposure and its non-regenerative reduction is responsible of the cell performance decrease. In agreement with the results of Carnie et al [9,11] and Hinsch et al [6], we have observed electrolyte solution bleaching when light soaking is performed without UV filter. To the nakedeye, the electrolyte solution became colorless after 2 days in the case of the templated cell while it is still yellow-colored for the nanoparticle cell.…”

“…As UV exposure leads to the cell degradation [1][2][3]6,8,9,11], a UV blocking filter (transmission 50% at 410 nm, purchased from UQG Optics) was applied to the cells during the light soaking tests. Efficiencies of the cells were measured every 2 days.…”

“…UV exposure has been proved to degrade DSSC performances [1][2][3]6,8,9,11]. TiO 2 is naturally active when irradiated with UV light, producing electron-hole pairs which can lead to the degradation of organic species such as dye molecules and electrolyte.…”

“…This drawback can be easily solved for both kinds of cells by the use of a UV filter, with an optimal cut-off wavelength of 400 nm [11]. Therefore UV exposure will not be considered further in this paper as a limiting factor of the stability of the DSSCs.…”

“…Dye photodegradation is controversial [4,6,9,10] [6,9,11] UV filters are often used to solve this problem. MgI 2 or CaI 2 can also be added to the electrolyte solution [6].…”