Enhancement of solar cell efficiency by spectral-conversion using rare earth-metal nanoclusters

A novel organic/inorganic nanocomposite is proposed as a luminescent material of a spectral converter (SC) for improving the energy conversion efficiency of solar cells. The nanocomposite consists of a polymer matrix doped with rare earth-centered heterometallic alkoxides, rare earth (RE)-metal (M) nanocluster. The excitation edge of Eu³⁺ was found to be extended from about 400 nm to 470 nm by adding Michler´s ketone to the nanocomposite. The broadening of the excitation wavelength range enhanced the energy conversion efficiency of a single-crystalline Si solar cell by 9.9%. Also it was found that Eu-M nanocluster can emit broad-band luminescence ranging from 400 nm to 600 nm in addition to the narrow-bands luminescence peculiar to Eu³⁺ when M is selected. Such controllability in both excitation and emission spectra could make it possible to use the nanocomposite doped with RE-M nanocluster as a luminescent material for SCs for various solar cells having different spectral responses.