External quantum efficiency, estimation

The electroluminescent (EL) properties of polymer 16 were examined by fabricating a standard EL device, ITO/PEDOT-PSS/lb/BCP/Alqj/LiF/Al (ITO=indium-tinoxide,PEDOT=poly(3,4-ethylenedioxythiophene),PSS=poly(4-styrenesulfonic acid), BCP=2,9-dimethyl-4,7-diphenyl-l,10-phenanfliroline, and Alq3=tris(8-hydroxyquinolinatojaluminum [26], The EL spectrum exhibited a maximum peak at around 490 mn with a tum-on voltage of 13 V. The luminescence brighmess was found to be 150 cd m- at a drive voltage of 19 V with a current density of 546 Am. The external quantum efficiency was estimated to be 0.88 % at 38 cd m under a bias of 14 V. Thus, we expect the application and development of [2.2] paracyclophane-based jt-stacked polymers in optoelectronic devices. 

Among other parameters the external quantum efficiency (EQE) can be estimated. EQE is defined as a ratio of the number of electrons in external circuit to the number of incident photons. To evaluate the EQE one measures the spectral response (SR) of the photovoltaic device (PVD) ... 

If the excited level Ej lies closely below the ionization limit, the molecule M (Ej ) can be ionized by an external electric DC field (Fig.6.20a). This method is particularly efficient if the excited level is a long-lived highly excited Rydberg state. The required minimum electric field can readily be estimated from Bohr s atomic model, which gives a good approximation for atomic levels with large principal quantum number n. The ionization potential for the outer electron at the mean radius r from the nucleus is determined by the Coulomb field of the nucleus shielded by the inner electron core. 

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