title: Effect of electrolyte bleaching on the stability and performance of dye solar cells.
abstract: Degradation of dye solar cells (DSCs) under severe ageing conditions may lead to loss of the tri-iodide in the electrolyte - a phenomenon known as electrolyte bleaching. Monitoring changes in the tri-iodide concentration as a result of degradation mechanisms and understanding their causes and effects are fundamental for improving the long-term stability of DSCs. In this contribution a strongly accelerated ageing test (1 Sun visible light, 1.5 Suns UV light, T = 110 °C for 12 h) was performed on DSCs in a double-sealed masterplate configuration to purposely induce severe electrolyte bleaching, and its effects on the performance and stability of DSCs with different initial tri-iodide concentrations [I3(-)]0 were investigated. The cells with low [I3(-)]0 suffered a severe loss in short circuit current density JSC (up to 85%). Also a significant loss of open circuit voltage VOC was observed and this loss was proportional to [I3(-)]0 with the highest VOC drop observed with the highest [I3(-)]0. Non-destructive analysis techniques based on the limited current density, JSCvs. light intensity, and photographic image analysis, were used to quantify the [I3(-)] loss, which was found to be ca. 50 mM and independent of [I3(-)]0. Quantitative model based VOC analysis in terms of changing [I3(-)] revealed that the degradation responsible for the VOC drop was dominated by an unknown mechanism that is unrelated to [I3(-)]0. The methods and results reported here help separating and identifying different degradation mechanisms related to electrolyte bleaching in DSCs.
authors.affiliation: Department of Electronics Engineering, CHOSE, Centre for Hybrid and Organic Solar Energy, University of Rome "Tor Vergata", Via del Politecnico 1, I-00133 Rome, Italy. thomas.brown@uniroma2.it.
authors.forename: Simone
authors.initials: S
authors.lastname: Mastroianni
authors.forename: Imran
authors.initials: I
authors.lastname: Asghar
authors.forename: Kati
authors.initials: K
authors.lastname: Miettunen
authors.forename: Janne
authors.initials: J
authors.lastname: Halme
authors.forename: Alessandro
authors.initials: A
authors.lastname: Lanuti
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Brown
authors.forename: Peter
authors.initials: P
authors.lastname: Lund