Luminescent concentration of sunlight onto high quality solar cells allows the manipulation and concentration of both direct and diffuse light for enhanced photovoltaic conversion efficiency. In addition, luminescence converts photons to spectral regions that are efficiently captured by the photovoltaic device. We utilize CdSe/CdS seeded nanorods as a tunable lumophore for luminescent concentration. These quantum rods are resistant to photobleaching, have high luminescent quantum yields, have tunable absorption and emission spectra, and have emission polarized along the nanorod axis. These nanorods are compatible with free-radical intiated polymers, facilitating ease of integration into large-area devices. Transfer-printed, ultrathin crystalline Si solar cells are embedded directly into the luminescent concentrator, allowing for mechanical flexibility. By tuning the size of the CdS rod with respect to the luminescent CdSe seed, the reabsorption of propagating photons is dramatically reduced. At long distances, this reduced reabsorption can overcome the diminished quantum yield inherent to the larger semiconductor structures, which is studied with lifetime spectroscopy. An accurate Monte-Carlo ray tracing model is developed to explain the performance of the luminescent concentrator, and is then used as a design tool to determine the upper limits of concentration using luminescent concentrators based on CdSe/CdS seeded nanorods. Exploring some hypothetical light-trapping scenarios, we show how an efficient light-trapping design can allow the LSC to operate in the high-concentration regime.

Luminescent concentration with semiconductor quantum rods and transfer-printed micro-silicon solar cells

247th National Meeting (2014)

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