Cell proliferation effect of deep-penetrating microcavity tandem NIR OLEDs with therapeutic trend analysis

Abstract

Long wavelengths that can deeply penetrate into human skin are required to maximize therapeutic effects. Hence, various studies on near-infrared organic light-emitting diodes (NIR OLEDs) have been conducted, and they have been applied in numerous fields. This paper presents a microcavity tandem NIR OLED with narrow full-width half-maximum (FWHM) (34 nm), high radiant emittance (> 5 mW/cm²) and external quantum efficiency (EQE) (19.17%). Only a few papers have reported on biomedical applications using the entire wavelength range of the visible and NIR regions. In particular, no biomedical application studies have been reported in the full wavelength region using OLEDs. Therefore, it is worth researching the therapeutic effects of using OLED, a next-generation light source, and analyzing trends for cell proliferation effects. Cell proliferation effects were observed in certain wavelength regions when B, G, R, and NIR OLEDs were used to irradiate human fibroblasts. The results of an in-vitro experiment indicated that the overall tendency of wavelengths is similar to that of the cytochrome c oxidase absorption spectrum of human fibroblasts. This is the first paper to report trends in the cell proliferation effects in all wavelength regions using OLEDs.

Figure 1

Device performance of non-cavity tandem OLEDs fabricated with various concentrations including a single OLED (reference): (a) Luminance-current density, (b) Efficacy-current density, and (c) Normalized EL spectra (experimental and simulation results).

Figure 2

XPS spectra of vacuum-deposited thin film (40 nm): (a) Alq₃ and (b) Alq₃:LiH (2 wt%) on ITO-patterned glass substrate.

Figure 3

Optical simulation values of 1st and 2nd cavity order of maximum intensity depending on the thickness of HTL(MoO₃ + NPB) and ETL(Alq₃) at each target wavelength of NIR OLEDs: (a) 710 nm, (b) 730 nm, (c) 750 nm, and (d) 770 nm. All the figures were generated using MATLAB.

Figure 4

Device characteristics of the microcavity single (a) and tandem devices (b,c): (a) current density–voltage, (b) luminance-current density, (c) efficacy-current density, (d) radiance-current density, (e) EQE-current density, and (f) normalized EL spectra of the single and tandem NIR OLEDs.

Figure 5

Cell effect in normal human fibroblasts (* $\le$ 0.05, ** $\le$ 0.01), values are mean percentage $\pm$ standard error of mean (n = 8): (a) cell viability and (b) cell proliferation over entire wavelength range. (c) cell proliferation in NIR wavelength range.

Figure 6

Tendency of cell proliferation for the entire wavelength region as a function of energy dose when irradiated by B, G, R, and NIR OLEDs. (Results indicated by purple circles are described in ref.)