Enhanced Quantum Cutting via Li + Doping from a Bi 3+ /Yb 3+ -Codoped Gadolinium Tungstate Phosphor

The Bi /Yb -codoped gadolinium tungstate phosphor has been synthesized through a solid-state reaction method. The structural characterization reveals the crystalline nature of the phosphor. The Bi -doped phosphor emits visible radiation from the blue to red regions upon excitation with 330 and 355 nm. The addition of Yb to the Bi -doped phosphor reduces the emission intensity in the visible region and emits an intense near-infrared (NIR) photon centered at 976 nm through a quantum-cutting (QC) phenomenon. This is due to cooperative energy transfer (CET) from the P level of Bi to the F level of Yb . The presence of Li ions in the Bi /Yb -codoped phosphor enhances the emission intensity in the NIR region up to by 3 times, whereas the emission intensity in the visible region is significantly reduced. The energy transfer (ET) from the Bi ions to the Yb ions is confirmed by lifetime measurements, and the lifetime for the P level of Bi decreases continuously with increasing Yb concentration. The ET efficiency (η ) and corresponding QC efficiency (η ) are calculated and found to be 29% and 129%, respectively. The presence of Li enhances the QC efficiency of the phosphor up to 43%. Thus, the Bi /Yb /Li -codoped phosphor is a promising candidate to enhance the efficiency of a crystalline-silicon-based solar cell through spectral conversion.