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Organic conjugated polymers and small molecules and their application in electronic devices like organic light emitting diodes, field-effect transistors and solar cells are thought to have definite advantages over their inorganic counterpart. These devices can potentially be cheaper and also suitable for large area applications. Organic solar cells in particular is being extensively investigated as a promising candidate for alternative energy technology and are
now reaching a power conversion efficiency of 10%. In this talk, I will discuss our research activities in this area where I will address few promising strategies to boost the performance of organic photovoltaic devices.
1. Effect of molecular order on charge transport and photoconductive property: The film-morphology of the polymer-fullerene blend influences the efficiency of a solar cell. Semiconducting polymers are long chain hydrocarbon materials which have a strong tendency to bend, twist and form coils in a solid state film. Under suitable processing conditions; high degree of molecular orientation can be achieved. We investigate whether, an uniaxial orientation of polymer chains in the direction of applied electric field can enhance the performance of the solar cell. A case of uniaxially oriented semicrystalline polymer and
its applications in lateral photodiode and field-effect transistor will be discussed in detail.
2. Novel device design and tandem solar cell: Second part of the talk will be focused on
fabrication of high efficiency tandem solar cells on optically opaque substrates. Based on
theoretical predictions from other groups, the efficiency of polymer tandem solar cells can
reach upto 15%. We fabricate and demonstrate first example of an top-illuminated ITO-free
tandem solar cell atop a metal surface with efficiency 6%. Top illumination in combination
with a structured reflecting metal bottom electrode can also enable future integration of
plasmonic or photonic light trapping structures in the metal electrode to enhance light
absorption.
References
1. D. Gupta et. al. Organic Electronics, 13, 36 (2012).
2. M. J. Lee et. al. Advanced Functional Materials, 21, 932 (2011).
3. D. Gupta et. al. Advanced Energy Materials, 3, 782 (2013). |