## 3 Calculation Results
In addition, we recently investigated the physical origin of the absorption loss based on the internal power flow of the air mode, where the absorption loss results from a part of the internal power flow of the air mode dissipated at the absorptive layer before the air mode is out-coupled into the air [25]. Thus, the variation in the relative radiative power of the absorption loss is similar to that in the relative radiative power of the out-coupled air mode as the dipole position is shifted. In Figure 5a, it is also observed that the TM-polarized relative radiative power of the SP mode is very close to total relative radiative power. Furthermore, the TM-polarized relative radiative power of the SP mode is almost identical to total relative radiative power in Figure 5b. According to Equation (36), the relative radiative power of the SP mode is obtained by integrating the spectral power density, shown in Figure 4, from \(u=1\) to infinity such that the optical power contribution of the SP mode is more significant than the other modes such as the air mode having the spectral range from \(u=0\) to \(u_{crit}\). In addition, according to the quantum-mechanical approach of the optical model of OLEDs, the optical power dissipation of each optical mode is determined by the amplitude of the electric field intensity at the emitter position and the photonic density of states of each optical mode [21]. In general, the SP mode has a relatively very large photonic density of states due to its very low group velocity [21]. Correspondingly, the contribution of the SP mode can be predominant in the TM-polarized relative radiative power. Similarly, the contribution of  
Figure 5: Calculated relative radiative powers of all the optical modes as a function of the dipole position in the EML for (**a**) a horizontally oriented dipole radiating TM-polarized light (TMh), (**b**) a vertically oriented dipole radiating TM-polarized light (TMv), (**c**) a horizontally oriented dipole radiating TE-polarized light (TEh), and (**d**) an isotropically oriented dipole. For the horizontally oriented dipole radiating TE-polarized light, the relative radiated powers of the SP mode and the NF absorption are not included because they cannot be excited by the horizontally oriented dipole in the TE-polarized light. the WG mode is very significant in the relative radiative power of the horizontally oriented dipole radiating TE-polarized light, shown in Figure 5c, because the photonic density of states of the WG mode is relatively very larger than that of the air mode. Finally, in the case of the vertically oriented dipole radiating TM-polarized light, its dipole radiation pattern designated in Equation (11) refers to a large value of \(u\), which corresponds to the spectral range of the SP mode [37, 38]. Hence, the relative radiative power of the SP mode is almost identical to total relative radiative power in Figure 5b. In Figure 5a,b, the TM-polarized relative radiative power emitted by the vertically oriented dipole is more coupled to the evanescent wave of SP modes and NF absorption than that radiated by the horizontally oriented dipole. On the other hand, the vertically oriented dipole provides smaller relative radiative power to both the out-coupled air mode and absorption loss than the horizontally oriented dipole does. This fact results from the angular radiation pattern of a Hertzian dipole emitter [12, 14, 22]. Regarding the out-coupled air mode and absorption loss, the relative radiative power emitted by the horizontally oriented dipole has the maximum intensities at the emitter positions of around 50 and 200 nm and the minimum intensity at the emitter position of around 130 nm. In contrast, the relative radiative power radiated from the vertically oriented dipole has the opposite emitter position of the maximum and minimum intensities.