Improved solar cell efficiency through the use of an additive nanostructure-based optical downshifter

This final report summarizes SpectraWatt's progress in achieving a boost in solar cell efficiency using an optical downshifter. Spectrawatt's downshifting technology is based on a nanostructured material system which absorbs high energy (short wavelength) light and reemits it at a lower energy (long wavelength) with high efficiency. This system has shown unprecedented performance parameters including near unity quantum yield and high thermal stability. The downshifter technology consists of a luminescent layer composed of chromophores embedded in a transparent matrix that is optically coupled to the solar cell. A fraction of the blue light incident on the luminescent material is absorbed by the chromophores (the fraction absorbed depends on chromophore loading) and re-emitted into the solar cell as red light. All other photons are absorbed by the solar cell directly. The chromophore that generates the optical properties is a Quantum Dot Heterostructure (QDH). Incorporation of the silica-encased QDH into PV encapsulants must be minimally disrupted to existing fabrication sequences of solar cell modules and, preferably, at no cost beyond that of the requisite materials.