Abstract
Liquid junction dye-sensitised solar cells (DSSCs) suffer from solvent evaporation and leakage which limit their large-scale production. Here, we have prepared DSSC using a simple and cheap fabrication process with improved photovoltaic parameters and stability. A binary mixture of Smectic A (SmA) and Nematic Liquid Crystal (NLC) was used to provide a self-assembled template for a polymerisable reactive mesogen LC. The layered structure of SmA combined with a low viscosity NLC forms a polygonal structure that provides an ordered and continuous template for reactive mesogens. Once the reactive mesogen is polymerised under UV light, the SmA:NLC mixture is washed away, resulting in a polymer network template containing nanochannels. We demonstrate the incorporation of these templates into DSSCs and find that DSSCs containing these nanochannels show improved open-circuit voltage (VOC) (0.705V) and short-circuit current (JSC) (13.25mAcm−2) compared to that of the liquid electrolyte (VOC=0.694V and JSC=10.46mAcm−2). The highest obtained power conversion efficiency with Sm-PE was 5.94% which is higher than that of the reference solar cell (5.51%). These can be attributed to the improved ionic conductivity and ionic diffusion of Sm-PE where the presence of the nanochannels aided the ionic conduction in the polymer electrolyte. In addition, it is hypothesized that the light scattering effect of the polymerised reactive mesogen also contributed to the improved performance of the photovoltaic devices. This finding is important because it is known fact that when a polymer is added to liquid electrolyte, the ionic conductivity will decrease although the stability is improved.
Highlights
Dye sensitised solar cells (DSSCs) were first demonstrated in 1991 by O’Reagan and Graetzel [1]
The molecules tend to align in layers. Despite their unique electro-optical properties that have allowed them to be used almost universally in display applications, LCs have had very limited use in photovoltaic applications. The exceptions to this has been work performed on the development of organic solar cells employing disc-like discotic liquid crystalline (DLCs) materials that have been shown to support higher charge carrier mobility than that of amorphous materials which is needed for a good electronic device [10,11]
We propose a new type of electrolyte, through the use of highly ordered Smectic A (SmA)/Nematic Liquid Crystal (NLC) mixture which provides a template for the assembly and alignment of Reactive mesogens (RMs) components
Summary
Dye sensitised solar cells (DSSCs) were first demonstrated in 1991 by O’Reagan and Graetzel [1]. Despite their unique electro-optical properties that have allowed them to be used almost universally in display applications, LCs have had very limited use in photovoltaic applications The exceptions to this has been work performed on the development of organic solar cells employing disc-like discotic liquid crystalline (DLCs) materials that have been shown to support higher charge carrier mobility than that of amorphous materials which is needed for a good electronic device [10,11]. Lim et al have shown that the templating technique can be used to prepare oxide semiconductors where block-graft copolymers were employed to prepare a highly organised TiO2 mesoporous layer [17] This approach has given the rise to the concept of utilising nanostructures with the redox electrolyte to improve the ionic conduction mechanism. The optimised binary LC mixture was used to fabricate DSSC and the photovoltaic properties are characterised
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