Abstract
Downconversion is a promising avenue to boost the efficiency of solar cells by absorbing one higher
energy visible photon and emitting two lower energy near-infrared NIR photons. Here the
efficiency of downconversion for the Er3+,Yb3+ couple is investigated in NaYF4, a well-known
host lattice for efficient upconversion with Er3+,Yb3+ . Analysis of the excitation and emission
spectra for NaYF4 doped with 1% Er3+ and codoped with 0%, 5%, 10%, or 30% Yb3+ show that
visible to NIR downconversion is inefficient. Downconversion by the scheme based on the reverse
of the upconversion process is hampered by fast multiphonon relaxation from the 4F7/2 level the
starting level for downconversion to the 4S3/2 level. Energy transfer from the 4S3/2 level of Er3+ to
Yb3+ is shown to be inefficient. Efficient downconversion from the 4G11/2 of Er3+ level is observed,
resulting in emission of two photons one around 980 nm and one around 650 nm after absorption
of a single 380 nm photon.
Original language | Undefined/Unknown |
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Pages (from-to) | 023522/1-023522/6 |
Number of pages | 6 |
Journal | Journal of Applied Physics |
Volume | 106 |
Issue number | 2 |
Publication status | Published - 2009 |