Electromagnetic Modeling of Outcoupling Efficiency and Light Emission in Near-Infrared Quantum Dot Light Emitting Devices

Abstract

Abstract-We report an analytical exciton emission model based on Green function for simulating the radiation characteristics of nearinfrared Quantum Dot-light emitting devices (QD-LEDs). In this model the internally emitted light can be classified into the following modes: Substrate, indium tin oxide (ITO)/organic waveguided, surface plasmonic modes, and external emitted mode. We investigate the influence of the thickness of different layers and the distance between the emitting center and the cathode metal on the emitted power distribution among these modes. In addition, we study the angular radiation profile for the externally emitted radiation and substrate waveguided mode in comparison with Lambertian radiation profile. We show the change of the thickness of the different layers, and the positions of the emitting centers are critical to the optical performance of the device. The optimization of optical performance through device geometry increases the outcoupling efficiency more than five times.

Anode material based on SWCNT for infrared quantum dot light-emitting devices

“…On other hand, we have investigated the effect of replacing ITO anode by the SWCNT on the outcoupled emission intensity. The outcoupled emission intensity is calculated as in Farghal et al (2010). Figure 8 shows the calculated outcoupled emission spectra in the IR region for glass/(160 nm) ITO/(40 nm) α-NPD/(20 nm) PbSe QD/(40 nm) Alq 3 /(50 nm) Mg:Ag/Ag and glass/(160 nm) SWCNT/(40 nm) α-NPD/(20 nm) PbSe QD/(40 nm) Alq 3 /(50 nm) Mg:Ag/Ag devices.…”

“…The simulations presented in this work are based on the Poynting vector analytical expression developed by Celebi et al (2007) and followed our computations for the IR QD-LEDs (Farghal et al 2010). Several other approaches for the simulation of OLEDs have been described in the literatures; for example, the radiative transfer approach which allows one to compute only the color (Crawford 1988;Bulović et al 1998) model which enables one to compute accurately the intensity, but only for simple device structures, Fermi's golden rule (Kahen 2001) which compute both the radiative and internal intensities, however, the validity of that approach is limited to lossless devices, and does not account for nonradiative losses to the metal electrodes or absorption, wave optics and transfer matrix formalism (Chen et al 2006), but they cannot be directly applied to OLEDs, because OLED uses a thick glass substrate, which results in computational difficulty, and the scheme described by Kahen (2001), is rigorous but not efficient, since the calculation involves the evaluation of the sommerfeld-like integral which requires careful selection of the integration path, in addition, accurate computation of the far-field at a large viewing angle is inefficient due to the rapid oscillating nature of Bessel function with the large argument.…”

The Effect of Electrode Materials on the Optical Characteristics of Infrared Quantum Dot-Light Emitting Devices

“…On other hand we have investigated the effect of replacing ITO anode by the SWCNT on the outcoupled emission intensity. The outcoupled emission intensity is calculated as in [11]. Figure 7 shows the calculated outcoupled emission spectra in the IR region for glass/ (160 nm) ITO/ (40 nm) α-NPD/(20 nm) PbSe QD/ (40 nm) Alq 3 / (50 nm) Mg:Ag/Ag and glass/ (160 nm) SWCNT/ (40 nm) α-NPD/ (20 nm) PbSe QD/(40 nm) Alq 3 / (50 nm) Mg:Ag/Ag devices.…”

“…The simulations presented in this work are based on the Poynting vector analytical expression developed by Celebi et al [10] and followed our computations for the IR QD-LEDs [11]. Several other approaches for the simulation of OLEDs have been described in the literatures; for example, the radiative transfer approach which allows one to compute only the color [12], Chance et al [13] model which enables one to compute accurately the intensity, but only for simple device structures, Fermi's golden rule [14] which compute both the radiative and internal intensities, however, the validity of that approach is limited to lossless devices, and does not account for nonradiative losses to the metal electrodes or absorption, wave optics and transfer matrix formalism [15], but they cannot be directly applied to OLEDs, because OLED uses a thick glass substrate, which results in computational difficulty, and the scheme described by Kahen [14], is rigorous but not efficient, since the calculation involves the evaluation of the Sommerfeld-like integral which requires careful selection of the integration path, in addition, accurate computation of the far-field at a large viewing angle is inefficient due to the rapid oscillating nature of bessel function with the large argument.…”

Electronic and excitonic processes in multilayer organic light emitting devices incorporating PbSe quantum dots

“…where I ∞ is the emission intensity at large capture limit (s → ∞), and the output coupling efficiency at each wavelength η oc (λ) of this structure is calculated using Green's function based model in our early work [21].…”