Co-doped NaYF4:Yb/Er/Tm upconversion luminescent coating to enhance the efficiency of photovoltaic cells

The use of upconversion luminescent materials to broaden the utilization range of the solar spectrum to enhance the efficiency of photovoltaic cells offers a promising and sustainable approach. However, the low luminescence intensity and easy quenching of upconversion luminescent materials bring serious challenges to the practical application. Herein, a novel method using Co2+ ion doping to regulate the luminescence properties of NaYF4:Yb/Er/Tm is proposed. NaYF4:Yb/Er/Tm microcrystals doped with different proportions of Co2+ ions are prepared and used as coatings on the surface of photovoltaic cells. Co2+ ions regulate the crystallinity and size of the NaYF4:Yb/Er/Tm microcrystals and reduce the crystal field symmetry of the activator (Er3+ and Tm3+) ions. The results show that the emission intensity of green and red light is 18.19% and 83.24% times higher than that of undoped Co2+ ion materials, respectively. Besides, the efficiency of photovoltaic cells after coating Co2+ ion doped NaYF4:Yb/Er/Tm is 2.08% higher than that of the uncoated one. This work underscores the importance of Co2+ ion doping to improve and enhance the luminescence properties of NaYF4:Yb/Er/Tm, to further enhance the efficiency of photovoltaic cells.

Fluorescence temperature sensing of NaYF4:Yb3+/Tm3+@NaGdF4:Nd3+/Yb3+ nanoparticles at low and high temperatures

NaYF₄:Yb³⁺/Tm³⁺@NaGdF₄:Nd³⁺/Yb³⁺upconversion nanoparticles were prepared using a solvothermal method, and the effects of key factors such as the content of sensitiser Nd³⁺and Yb³⁺on their luminescence properties were investigated. The nanoparticles are homogeneous in size and well dispersed. Under 808 nm excitation, it can produce strong upconversion fluorescence. At the same time, the nanoparticles have good temperature sensing properties at the thermally coupled energy levels of 700 and 646 nm for Tm³⁺. Using its fluorescence intensity ratio, accurate temperature measurements can be performed, and it has been found that it exhibits different temperature sensing properties in low and high-temperature regions. The maximum relative sensitivity was found to be 0.88% K^-1and 1.89% K^-1for the low-temperature region of 285-345 K and the high-temperature region of 345-495 K. The nanoparticles were applied to the internal temperature measurement of lithium batteries and the actual high-temperature environment, respectively, and were found to have good temperature measurement performance.

The role of 2-ethylhexanoic acid in manipulating the morphology and upconversion of flame-made Y2O3:Yb3+/Ho3+ nanoparticles towards remote temperature sensing

In the flame spray pyrolysis process, 2-ethylhexanoic acid manipulates morphology of Yb3+/Ho3+ co-doped Y2O3 upconversion nanoparticles towards homogeneous and ultrafine but causing upconversion luminescence quenching and thermal sensitivity lowering.

Effect of Ca2+ doping on the upconversion luminescence properties of NaYF4:Yb3+/Tm3+ nanoparticles and its application to fluorescence temperature characteristics

The solvothermal method prepared a series of Yb3+/Tm3+/Ca2+ co-doped NaYF4 nanoparticles with different Ca2+ contents. Strong upconversion blue fluorescence could be observed under 980 nm laser excitation of the samples....