Paper
Abstract The near‐infrared (NIR) down‐conversion process for broadband sensitization has been studied in Eu 2+ ‐Nd 3+ co‐doped BaAl 2 O 4 . This material has a broad absorption band of 200–480 nm and can convert photons in the visible region into NIR photons. The NIR emission at 1064 nm, attributed to the Nd 3+ : 4 F 3/2 → 4 I 11/2 transition, matches the bandgap of Si, allowing Si solar cells to utilize the solar spectrum better. The energy transfer (ET) process between Eu 2+ and Nd 3+ was demonstrated using photoluminescence spectra and luminescence decay curves, and Eu 2+ may transfer energy to Nd 3+ through the cooperative energy transfer (CET) to achieve the down‐conversion process. The energy transfer efficiency (ETE) and theoretical quantum efficiency (QE) were 68.61% and 156.34%, respectively, when 4 mol% Nd 3+ was introduced. The results indicate that BaAl 2 O 4 :Eu 2+ ‐Nd 3+ can serve as a potential modulator of the solar spectrum and is expected to be applied to Si solar cells.