Lead Selenide Quantum Dot Luminescent Solar Concentrators

Worldwide photovoltaic energy generation capacity is expected to double or triple 2013 levels by 2018. There is thus considerable motivation to reduce the cost of photovoltaic energy generation. Luminescent solar concentrators (LSCs) have the potential to reduce the price per Watt of solar power. LSCs operate by efficiently capturing sunlight over a broad spectrum using a fluorescent molecule such as dyes or quantum dots. The emitted fluorescent light is guided in a polymer matrix to the edges where a photovoltaic cell is attached for optical to electric power conversion. So, fluorescent dyes or quantum dots play an important role for efficient solar power conversion.

Here, functionalized, high quantum yield (> 70%) lead selenide quantum dots (PbSe QDs) are investigated for use in LSCs to replace dyes as the luminescent molecule. PbSe QDs have a much wider absorption spectrum than dyes, and so are able to absorb more incident solar radiation. Individual optical losses in LSCs are characterized. These losses and routes to LSC optimization are investigated with a custom ray tracing model.

A method of incorporating QDs into an AB9093 epoxy or a poly(lauryl methacrylate-co-ethylene glycol dimethacrylate) polymer matrix is presented, as well as a discussion of other matrix candidates. The resulting QD nanocomposite optical absorption and fluorescence properties at room temperature were studied, and their properties in an AB9093 matrix were characterized as a function of temperature from 0°C to 80°C and compared to QDs in a toluene solution. A decrease in fluorescence intensity was found as temperature increased.

A nanocomposite LSC was fabricated and mated with a monocrystalline silicon photovoltaic cell. The resulting system had a power conversion efficiency (PCE) of 4.93% measured under one sun broadband illumination. This is the highest known broadband PCE of any LSC system using either silicon photovoltaic cells or QDs of any kind.