title: Assessment of luminescent downshifting layers for the improvement of light-harvesting efficiency in dye-sensitized solar cells.
abstract: Luminescence downshifting (LDS) of light can be a practical photon management technique to compensate the narrow absorption band of high-extinction-coefficient dyes in dye-sensitized solar cells (DSSCs). Herein, an optical analysis on the loss mechanisms in a reflective LDS (R-LDS)/DSSC configuration is reported. For squaraine dye (550-700 nm absorption band) and CaAlSiN3 :Eu(2+) LDS material (550-700 nm emission band), the major loss channels are found to be non-unity luminescence quantum efficiency (QE) and electrolyte absorption. By using an ideal LDS layer (QE=100 %), a less absorbing electrolyte (Co-based), and antireflection coatings, approximately 20 % better light harvesting is obtained. If the absorption/emission band of dye/LDS is shifted to 800 nm, a maximal short-circuit current density (Jsc ) of 22.1 mA cm(-2) can be achieved. By putting the LDS layer in front of the DSSC (transmissive mode), more significant loss channels are observed, and hence a lower overall efficiency than the R-LDS configuration.
authors.affiliation: Institute for Nanoscience and Nanotechnology, Sharif University of Technology, Tehran 14588 (Iran).
authors.forename: Zahra
authors.initials: Z
authors.lastname: Hosseini
authors.forename: Eric Wei-Guang
authors.initials: EW
authors.lastname: Diau
authors.forename: Khashayar
authors.initials: K
authors.lastname: Mehrany
authors.forename: Nima
authors.initials: N
authors.lastname: Taghavinia
keywords: dye-sensitized solar cells; dyes/pigments; luminescent down shifting; optical modeling; phosphors