Efficient visible/ultraviolet to near-infrared quantum cutting emission and charge transfer/upconversion luminescence in Pr3+/Yb3+ co-doped CaLaAl3O7 phosphors

Quantum cutting in the near-infrared (NIR) region offers an effective strategy for enhancing the photoelectric conversion efficiency of silicon-based (c-Si) solar cells. However, developing materials capable of simultaneously converting visible and ultraviolet (UV) light into NIR emission remains a major challenge. Matching the energy gap between Pr 3+ 3 P j (j = 0, 1, and 2) and Yb 3+ 2 F 7/2 levels enables resonance energy transfer (ET), resulting in efficient quantum cutting and upconverted emissions. In this study, a series of CaLaAl 3 O 7 :Pr 3+ /Yb 3+ phosphors was prepared via high-temperature solid-state reactions. Upon excitation at 450 and 250 nm, Pr 3+ /Yb 3+ co-doped phosphors demonstrated downshifted emission peaks at 484, 526, 548, 594, 604, 615, 644, and 728 nm, attributed to the 3 P 0 → 3 H 4 , 3 P 0 → 3 H 5 , 3 P 1 → 3 H 5 , 3 P 1 → 3 H 6 , 1 D 2 → 3 H 4 , 3 P 0 → 3 H 6 , 3 P 0 → 3 F 2 , and 3 P 0 → 3 F 4 transitions of Pr 3+ , respectively. Moreover, under 450 nm excitation, an intense NIR emission was observed at 980 nm, resulting from ET from Pr 3+ to Yb 3+ , and the quantum cutting efficiency ( ) for the 3 P 0 → 3 F 2 transition becomes 190% at a Yb 3+ concentration of 20%. Meanwhile, the quantum cutting efficiency ( ) for the 3 P 0 → 3 H 4 transition becomes 189% at a Yb 3+ concentration of 20% under 250 nm excitation. Notably, the CaLaAl 3 O 7 single-doped Yb 3+ sample demonstrated intense charge transfer luminescence under 257 nm excitation. Temperature-dependent spectral measurements revealed that the materials possess excellent thermal stability. Furthermore, under 980 nm NIR excitation, characteristic visible-light luminescence of Pr 3+ was observed. The fitted slope of the upconversion luminescence intensity as a function of laser pump power density was n 460-516 = 2.36, indicating a two-photon absorption upconversion process. These materials have the potential to not only enhance the photoelectric conversion efficiency of silicon-based solar cells but also mitigate excessive heating of silicon-based space cells under intense UV irradiation.