Here are two baggies of up-shift crystalline phosphors with a IR laser directly illuminating them, they are really bright ,but the IR laser is actually invisible to the human eye. It is important to note that you need to keep the power down on a IR laser well below 5 mw, preferably around 1 mw because your eyes will not blink in response to the bright laser emission. One way I intend on lowering the output is PWM, second is to put a star filter over the diode to disperse the laser light in a much wider area making it more useful to illuminate the QR codes.

https://en.wikipedia.org/wiki/Stokes_shift

"If the emitted photon has more energy, the energy difference is called an anti-Stokes shift;^[5] this extra energy comes from dissipation of thermal phonons in a crystal lattice, cooling the crystal in the process. Yttrium oxysulfide doped with gadolinium oxysulfide is a common industrial anti-Stokes pigment, absorbing in the near-infrared and emitting in the visible region of the spectrum. Photon upconversion is another anti-Stokes process. An example of this later process is demonstrated by upconverting nanoparticles."

crystalline latices powdered pigments can augment existing ink carriers so that invisible codes, glyph or even April codes can be excited by a laser indoors.