Apr
11

Diatomaceous Hybrid Nanoparticle/Polymer Solar Cells

The most ideal source of sustainable, environmentally friendly energy is solar power; however, current solar-cell devices are expensive, inefficient, and often use toxic substrates in their production. The current method to process silicon, the most common material used in solar cells, is tedious and expensive. Because of their cost, solar cells are still not a feasible addition for many households. Meanwhile, floating within almost every body of water on the planet, a species of single-cellular algae called the diatom has spent millennia fine-tuning its own ability to capture solar energy. The diatom’s cell wall, known as a frustule, is made out of amorphous bio-silica. The frustule’s mechanical strength, complex 3D structure, multilevel nanopores, and large surface area make it a potentially novel material for integration into solar cells.  In addition, the frustule has many unique optical properties. The sophisticated, porous structure of the frustrule has been shown to couple incoming light into distinct photonic bandgaps and thus acts as a living photonic crystal. Based on this, and other previous research, it has been hypothesized that the inexpensive diatom could revolutionize the ways in which photovoltaic (PV) energy devices are manufactured. I would like to explore the ways in which diatoms could be used to inexpensively solve the efficiency problems currently facing one of the most low-cost types of solar cells on the market: the Hybrid Nanoparticle/Polymer cell.

Hybrid SCs have the potential to be one of the most cost-effective SCs on the market; however, they have been unsuccessful at reaching efficiencies that allow them to be economically competitive so far. This is largely due to assembly problems with the active layer; nanoparticles that are used to transport electrons through the active layer continue to clump together (aggregate) as the active layer is assembled. To reach maximum efficiency, the nanoparticles must be evenly dispersed throughout the polymer and form a continuous network for electron transport. Currently, the only way to achieve this particular structure is to use stabilizing ligands during the preparation of the active layer. Unfortunately these ligands are insulating and provide a barrier to charge transport.  Upon comparison of the structure of the diatom frustule and the ideal dispersion pattern of the nanoparticles, I hypothesized that nanoparticles formed either inside of the pores of the diatom or along the diatom’s surface could provide this hierarchical and constant structure without the need for insulating ligands. In addition, the diatom’s unique optical properties could trap photons in the active layer, giving the SC a higher optical absorption than other traditional first-generation solar panels.  This would allow for increased efficiencies while still using simplistic, low temperature production methods. Finally, one of the most exciting prospectives of the diatomaceous Hybrid SC is that both the material of the nanoparticles, the silica frustrule and the polymer all have the potential to act as donors. This means that this style of SC has the potential for broad band absorption, and could function in low light conditions by absorbing photons well into the UV spectrum.

 

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