Two Colour Excitation Up-Conversion Efficiency Enhancement for a Silicon Photovoltaic Device using Er3+-Doped Phosphors

This paper summarises the dominant up-conversion (UC) mechanisms of single wavelength illumination of Er³⁺ doped phosphors. The excitation spectra for three separate UC mechanisms are shown not to overlap with the absorption band of the higher level(s) (2-step) of the Er³⁺ ions. Higher UC efficiencies are more probable using at least two separate light energies directly pumping the required levels of the Er³⁺ ions via ground state absorption/excited state absorption (GSA/ESA) mechanisms. The dominant up-conversion mechanism under two-colour excitation using Er³⁺ doped phosphors is investigated and the spectral robustness of a photovoltaic-upconversion (PV-UC) device is analysed. The resulting dependence of the excited intermediate level on incident pump power is also discussed