Upconversion luminescence thermal enhancement from visible to near infrared and improving temperature sensitivity under high temperature using second-harmonic generation response

Er3+/Nd3+co-doped and Er3+/Yb3+/Nd3+triple-doped Cs2Bi2Sr(P2O7)(PO4)2(CBSP) phosphors are prepared by solid state reaction, and upconversion luminescence (UCL) from visible to near infrared was investigated under 808, 980 and 1550 nm laser excitations, respectively. UCL of Er3+and Nd3+manifests thermal enhancement under 808, 980 and 1550 nm excitations, respectively, except for under 980 nm laser excitation, Er3+/Nd3+co-doped sample exhibits UCL thermal quenching of Er3+. This thermal enhancement phenomenon has been discussed and attributed to phonon-assisted energy transfer and electron thermal migration. The relative temperature sensitivities were calculated based on LIR technique under 980 and 1550 nm laser excitations, respectively. Under 1550 nm laser excitation, using second-harmonic generation (SHG) response improved the temperature sensitivity in high temperature range, and the two maximum sensitivities at low and high temperature are obtained as 0.0062 K-1at 484 K and 0.0111 K-1at 697 K; 0.0219 K-1at 303 K and 0.0097 K-1at 555 K for Er3+/Nd3+co-doped and Er3+/Yb3+/Nd3+triple-doped samples, respectively. UCL thermal enhancement and using SHG response provide a new approach for improving the sensitivity as optical thermometer under high temperature.