Controllable planar electrodeposition of NaYF4: Yb3+, Er3+ thin films with efficient upconverting fluorescence

The lanthanide doped NaYF4, one of the most efficient upconverting materials, which shows great potential in the applications of future optoelectronic devices. Although there are many progress on the synthesis and performance modulations of upconversion fluorescence single crystal and nanoparticles, it is still a great challenge to fabricate upconverting thin film to compatible with modern planar silicon photoelectronic devices. In this work, patterned NaYF4: Yb3+, Er3+ thin films were prepared by a well-designed strategy combined with photolithography and electrodeposition at 50 °C. The thickness of NaYF4: Yb3+, Er3+ thin films could be modulated from 1.6 ± 0.3 to 6.1 ± 0.4 μm by the deposition time. After the further annealing at 300 °C, the NaYF4: Yb3+, Er3+ thin films present efficient green upconversion fluorescence with fine spectra from 510 to 720 nm, which resulted from the electronic transitions of doped Er3+ ions. The application of laser direct-writing mask could introduce the desired micropattern of NaYF4: Yb3+, Er3+ thin films, which show uniform distributed green upconversion fluorescence pixel with fine resolution of about 50 μm. The intense upconversion luminescence pattern with high spatial resolution show great application potential in the fields of displays, photodetectors, biological sensors, solar energy converter and commercial anticounterfeiting.