We developed an integrated monochromatic excitation light source integrating sphere based detection system to accurately characterize the absolute photoluminescence quantum efficiency of commonly used polymer light emitting films without using a reference sample. Our methodology is similar to the method reported by de Mello et al. [Adv. Mater. 9, 230 (1997)] In this Note, we show that the absolute photoluminescence quantum efficiency might only be measured when an appropriate calibration of the spectral variation of the measurement system is done. This calibration is especially important when employing a short excitation wavelength (<400 nm) for common silicon-based detector.
Abstract— The optoelectronic properties of red, green, and blue poly(fluorene) co‐polymer light‐emitting devices (PLEDs) on a plastic substrate having a multi‐layered structure with water vapor and oxygen transmission rates of less than 10−5 g/cm2‐day‐atm and 10−7 cc/cm2‐day‐atm, respectively, is reported. A semitransparent thin metal multi‐layer (i.e., Au/Ag/Au or Ag/Au/Ag) is placed between the plastic substrate and the ITO coating, achieving a low sheet resistance of 12–13 Ω/□ and an adequate optical transmission greater than 75%. A wider color gamut and a maximum emission efficiency of 0.7, 10, and 1.7 cd/A for red, green, and blue PLEDs, respectively, was obtained. Finally, a simple equivalent‐circuit model was used to simulate the current‐density—voltage characteristics of PLEDs.
A Monte Carlo method for modeling the light transport phenomena in organic polymer light-emitting devices (PLEDs) is reported. In this simulation we assumed a point light source having photon emission spectrum represented by the photoluminescence (PL) spectrum of the organic polymers. This method describes the fate of photons through multiple scattering events determined by the wavelength-dependent material optical properties in a 3-D Cartesian geometry, thus considering the effects of refraction at different interfaces, back-reflection from the cathode, interference effect in the ITO thin film, and absorption within the polymer layers. We apply this method to analyze the wavelength output distribution and extraction efficiency. We found that the simulated light emission spectra of the green and red light-emitting devices are very similar to the measured PL spectra, suggesting that the light transport phenomena do not change the energy distribution significantly. We also established that the calculated extraction efficiency for the red ( ext η =19.5%) and green ( ext η =19.9%) PLEDs are approximately the same. We further investigated the light emission angular distribution of the PLEDs, and found that the simulated angular distribution shows better agreement with the experimental data than previously used models that rely on standard refraction theory at one interface.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.