Long-term stability of dye solar cells
Introduction
Dye solar cells (DSC) offer attractive performance at an affordable cost, superior performance under diffuse or otherwise non-ideal light conditions, tunable colouration and/or transparency, flexibility, low weight and low embodied energy. Since the early days of DSC (Desilvestro et al., 1985, O’Regan and Grätzel, 1991), efficiency has continually been improved for laboratory cells to presently 12.2% (Grätzel, 2009), rendering this technology increasingly competitive for practical applications. In order to be successful in the market place, any novel photovoltaic technology has to offer a favourable performance-to-cost ratio and sufficient product durability. For commercially viable building integrated applications, panel life time needs to be 20–25 years. As with any PV technology, a variety of mechanisms can lead to loss of performance over extended periods of time. In the case of DSC, where the principle of operation is based on molecular processes, similar to photosynthesis, some of the mechanisms for loss of performance are fundamentally different from those occurring in other solid-state devices based on p-/n-junctions. This paper will review the main degradation mechanisms in DSC and then present some recent results with industrial type cells.
Section snippets
Review of mechanisms for loss of performance
Degradation can occur at four different levels, i.e. the molecular, cell, module/panel, and system level. Every level is characterised by higher complexity and relies on stability of the lower levels. This study will mainly deal with the molecular and cell aspects.
Materials and preparation of cells
All chemicals used in this work were stored in a dry room (relative humidity ∼2%) and used without any further purification. “Solvent based” electrolyte solutions contained 1-propyl-3-methylimidazolium iodide (PMII, >99%, Merck), iodine (I2, 99.8%, Aldrich) and guanidinium thiocyanate (99.9%, Fluka) in 3-methoxypropionitrile (MPN, 99+%, Fluka). Benzimidazole was used to control titania surface charge in solvent based electrolyte systems to a certain extent. Alternatively, some comparative tests
Light soaking of single cells under resistive load
Materials and dimensions for cells assembled and investigated in this work were all selected in respect to their industrial relevance. Thus only relatively non-volatile and non-toxic electrolyte components were employed and relatively low cost TEC 15 conductive glass was employed. In contrast to many researchers who use ‘spot cells’ of <0.2 cm2 size, where currents and thus resistive losses are small and therefore fill factor and efficiency high, we use dimensions which are representative for
Conclusions
In summary, the results highlighted in this work clearly demonstrate the prospects of DSC technology for extended product with some reservations yet concerning exposure to temperatures above 80 °C continuously. Therefore, applications in moderate climates, e.g. Northern and Middle Europe, but also in situations where the angle of incidence of solar light is not optimum, such as on façades, appear to be ideally suited for DSC market introduction.
Detailed analysis from light soaking data at 55–60
Acknowledgements
The authors thank Dyesol Limited and numerous members of the team for materials preparation, establishment and maintenance of infrastructure and equipment and for funding this work.
References (49)
- et al.
Anodic oxidation of propylene carbonate and ethylene carbonate on graphite electrodes
J. Power Sources
(1995) Photovoltaic performance and long-term stability of dye-sensitized meosocopic solar cells
C. R. Chim.
(2006)- et al.
Accelerated aging for testing polymeric biomaterials and medical devices
Med. Eng. Phys.
(2008) - et al.
Degradation analysis of dye-sensitized solar cell module after long-term stability test under outdoor working condition
Sol. Energy Mater. Sol. Cells
(2009) - et al.
In-situ FTIR study of anodic photoreactions at the n-TiO2, (anatase) electrode in aprotic electrolyte solutions
J. Electroanal. Chem.
(1994) - et al.
(Photo) anodic decomposition of 3-methyl oxazolidin-2-one. An in-situ FTIR study
J. Electroanal. Chem.
(1997) - et al.
Thermal thiocyanate ligand substitution kinetics of the solar cell dye N719 by acetonitrile, 3-methoxypropionitrile, and 4-tert-butylpyridine
Sol. Energy Mater. Sol. Cells
(2007) - et al.
Dissolution of platinum in methoxy propionitrile containing LiI/I2
Sol. Energy Mater. Sol. Cells
(2000) - et al.
Long-term stability of low-power dye-sensitised solar cells prepared by industrial methods
Sol. Energy Mater. Sol. Cells
(2001) - et al.
A glass frit-sealed dye solar cell module with integrated series connections
Sol. Energy Mater. Sol. Cells
(2006)