Ce3+ → Pr3+ energy transfer and traps boosting thermal stability of KSrScSi2O7: Ce3+, Pr3+ phosphor for full-spectrum solid-state lighting

This work studied the Pr 3+ single doped KSrScSi 2 O 7 : x Pr 3+ ( x  = 0–10 at%) and Ce 3+ -Pr 3+ codoped KSrScSi 2 O 7 : Ce 3+ , y Pr 3+ ( y  = 0.5–7 at%) phosphors, including photoluminescence characteristics, crystal structure, and the mechanism of Ce 3+ → Pr 3+ energy transfer. All the samples were synthesized by the high-temperature solid-phase method. Under 448 nm light excitation, the KSrScSi 2 O 7 : x Pr 3+ ( x  = 0.5–10 at%) phosphors emitted narrow-band cyan-blue light (490 nm, 3 P 0 → 3 H 4 ), green light (530 nm, 3 P 1 → 3 H 5 ), orange-red light (605 nm, 1 D 2 → 3 H 4 and 3 P 0 → 3 H 6 ), and red light (645 nm, 3 P 0 → 3 F 2 ). The KSrScSi 2 O 7 : 3 at%Ce 3+ , y Pr 3+ ( y  = 1–7 at%) phosphors exhibited broad-band (380–550 nm) luminescence of Ce 3+ and narrow-band luminescence of Pr 3+ under 365 nm light excitation. In comparison with KSrScSi 2 O 7 : 3 at% Ce 3+ , the doping of 3 at% Pr 3+ beneficially enhanced the thermal stability of the phosphor (I 423 K /I 298 K from 37.4 % to 48.6 %), which was attributed to the introduction of electron trap by Pr 3+ . Through trapping energy levels compensation, the thermal stability of the phosphor was improved. By measuring the fluorescence decay kinetics of Ce 3+ in KSrScSi 2 O 7 : 3 at% Ce 3+ , y Pr 3+ ( y  = 0–7 at%), we have proved the existence of Ce 3+ → Pr 3+ energy transfer, whose efficiency rises from 42.8 % to 67.2 % along with increasing Pr 3+ concentration. A pc-WLED was fabricated by combining KSrScSi 2 O 7 : 3 at% Ce 3+ , 3 at% Pr 3+ with commercial red and green phosphors, and the device showed a high color rendering index (CRI = 94.8) and superior color rendering stability.