**3. Properties of the deposited films**

### **3.1. Crystalline structure of the inorganic additives in the polymer nano-composite film**

In order to conduct X-ray diffraction spectroscopy, the deposited films were separated from the substrates and placed in a Bruker D2 Phaser X-ray diffractometer. A reference sample of the PMMA nano-composite film containing only one upconversion phosphor additive was also made. The X-ray diffraction spectrum of this sample is presented in **Figure 10**. The spectrum has all the signatures of the hexagonal *β*-phase NaYF4 that was initially present in the first PLD target made of the upconversion phosphor. **Figure 11** shows the X-ray diffraction spectrum of the polymer nano-composite film including nanoparticles of both inorganic additives: the upconversion phosphor and AZO. The observed spectral peaks include those that can be attributed to both *β*-phase NaYF4 and AZO. It thus can be concluded that the two inorganic additives have been transferred to the polymer film without modification of their crystalline structure during the PLD process.

**Figure 10.** XRD spectrum of the two-component composite film made of PMMA and the nanoparticles of NaYF4: Yb3+, Er3+ with the diffraction peaks attributed to the hexagonal *β*-phase of NaYF4.

**Figure 11.** XRD spectrum of the three-component composite film made of PMMA and the nanoparticles of NaYF4: Yb3+, Er3+and AZO.
