1. Enhanced Stability for Dye-Sensitized Solar Cells
Conclusions:
The tested high boiling point liquid electrolyte (livion 12) reduces the thermal induced degradation in DSCs [2] by showing an efficiency degradation rate of about
-7.58%/1000h (Fig. 2.a and 2.b), which complies with the certification rules for photovoltaic market.
During thermal stress any sign of sealing breakage or electrolyte solution leakage was not detected. The residual decrease in efficiency can be imputable to a depletion in the free triiodide concentration [3] (Fig. 3.a and 3.b) and to the formation of degradation products within the electrolyte solution (Fig. 2.d) [4] probed by mean of micro-Raman spectroscopy.
The investigated devices have been demonstrated to be stable under thermal stress, providing a viable route in developing large area DSC production.
Degradation of DSCs :
Acknowledgement: The research leading to these results has received funding from the European Union Seventh Framework Program [FP7/ ] under Grant Agreement My sincere thanks to Alessandro Lanuti for his kind guidance during this research.
Figure 2. (a) J-V curve of Z907/L12, measured at 1 sun, for fresh and thermally stressed (4700 hours) devices. (b) Device electrical performance evolution during aging time 85°C) in terms of normalized efficiency, Jsc, Voc and fill factor, measured under 1 SUN illumination. (c) Devices efficiency of fresh (dark grey) and aged (light grey) cells in the same master-plate. (d) micro-Raman spectra of of fresh (curve a) and aged (curve b) electrolyte solution), acquired by focusing the laser beam onto the electrolyte monitor window.
Surendra K. Yadav, Antonio Agresti, Sara Pescetelli, Lucio Cinà, Desireé Gentilini, Aldo Di Carlo
C.H.O.S.E. (Centre for Hybrid and Organic Solar Energy),
Department of Electronic Engineering, University of Rome Tor Vergata, via del Politecnico 1, Rome, Italy. ,
References:
B. O’Regan, M. Grätzel, “Low-cost high-efficiency solar cell based on dye-sensitized colloidal TiO2 films”, Nature, 353, pp , 1991.
D. Perganti, A. G. Kontos, T. Stergiopoulos, V. Likodimos, J. Farnell, D. Milliken, H. Desilvestro, P. Falaras, “Thermal Stressing of Dye Sensitized Solar Cells Employing Robust Redox Electrolytes”, Electrochimica Acta,
A. Quatela, A. Agresti, S. Mastroianni, S. Pescetelli, T. M. Brown, A. Reale, A. Di Carlo, “Fabrication and Reliability of Dye solar Cells: A Resonance Raman Scattering study”, Microelectronics Reliability 52, pp , 2012.
A. Agresti, S. Pescetelli, E. Gatto, M. Venanzi, A. Di Carlo, “Polyiodides formation in solvent based Dye Sensitized Solar Cells under Reverse Bias Stress”, Journal of Power Sources 287, pp , 2015.
The device fabrication have been detailed in the “schematic” section. The master plate containing five equal solar cells was subjected to thermal stress at 85˚C in dark condition, for 4700 hours.
To investigate the thermal induced degradation mechanisms, the electrical parameters of device were extracted from the current density-voltage (J-V) characteristics recorded at 1 SUN illumination condition, at different stages during stress test.
Raman spectra were acquired for fresh and aged cells through confocal micro-Raman system equipped with Ar+ ion laser (514 nm) as excitation source (0.26 mW/μ2 on the scanned area ).
Experimental Details:
Figure 1. Schematic representation of device architecture and fabrication protocol for encapsulated devices subjected to stability tests. Actual master plate in background.
Abstract:
This work provides further insight on the long term stability of Dye Sensitized Solar Cells (DSCs) [1] assessed through prolong thermal aging at 85°C in the dark. The investigation is focused on Bis(isothiocyanate)(4,4'-dicarboxylate-2,2'-bipyridine)(4,4'-dinonyl-2,2'-bipyridine)ruthenium(II) (Z907) sensitized devices employing commercially available, high boiling point ionic liquid electrolyte (livion 12, L12). The electrical performance (measured under 1 Sun irradiation condition; 1000 W/m2) of the investigated device Z907/L12 degrades with a rate of -7.58x10-5/hours. The reported results are undoubtedly interesting in the optic of a feasible commercialization for DSCs technology.
Schematic:
Results for fresh and Aged cells :
FTO
TiO2
Dye
Electrolyte
Silver Contacts
Active Area
Electrolyte Window
Sealing Pt
(a)
(b)
(a)
(b)
(c)
(d)
Figure 3. (a) Micro-Raman spectra of a) fresh, b) thermal stressed cells (4700 hours of stress). (b) Low and high frequency region of Raman spectra of fresh (curve a) and aged (curve b) devices, extracted by Raman spectra reported in (a).