The realization of fully solution processed multilayer polymer light‐emitting diodes (PLEDs) constitutes the pivotal point to push PLED technology to its full potential. Herein, a fully solution processed triple‐layer PLED realized by combining two different deposition strategies is presented. The approach allows a successive deposition of more than two polymeric layers without extensively redissolving already present layers. For that purpose, a poly(9,9‐dioctyl‐fluorene‐co‐N‐(4‐butylphenyl)‐diphenylamine) (TFB) layer is stabilized by a hard‐bake process as hole transport layer on top of poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS). As emitting layer, a deep blue emitting pyrene‐triphenylamine copolymer is deposited from toluene solution. To complete the device assembly 9,9‐bis(3‐(5′,6′‐bis(4‐(polyethylene glycol)phenyl)‐[1,1′:4′,1″‐terphenyl]‐2′‐yl)propyl)‐9′,9′‐dioctyl‐2,7‐polyfluorene (PEGPF), a novel polyfluorene‐type polymer with polar sidechains, which acts as the electron transport layer, is deposited from methanol in an orthogonal solvent approach. Atomic force microscopy verifies that all deposited layers stay perfectly intact with respect to morphology and layer thickness upon multiple solvent treatments. Photoelectron spectroscopy reveals that the offsets of the respective frontier energy levels at the individual polymer interfaces lead to a charge carrier confinement in the emitting layer, thus enhancing the exciton formation probability in the device stack. The solution processed PLED‐stack exhibits bright blue light emission with a maximum luminance of 16 540 cd m−2 and a maximum device efficiency of 1.42 cd A−1, which denotes a five‐fold increase compared to corresponding single‐layer devices and demonstrates the potential of the presented concept.

The two-dimensional diffusion of isolated molecular tracers at the water-n-alkane interface was studied with fluorescence correlation spectroscopy. The interfacial diffusion coefficients of larger tracers with a hydrodynamic radius of 4.0 nm agreed well with the values calculated from the macroscopic viscosities of the two bulk phases. However, for small molecule tracers with hydrodynamic radii of only 1.0 and 0.6 nm, notable deviations were observed, indicating the existence of an interfacial region with reduced effective viscosity and increased mobility.

By contrast with the aminomethylation of thiourea by formaldehyde and primary amines to form 5-substituted 1,3,5-triazinane-2-thiones (see studies [1,2] and references therein) the aminomethylation of urea has not attracted so much work [3-10], the most recent being published in 1991. Because of the possibility of different condensations involving urea and formaldehyde [11,12] cyclic urea Mannich bases are better obtained not by a three-component condensation of urea, formaldehyde, and the corresponding primary amine [3-5, 7] but rather using 1,3-dimethylolurea (DMU) (1) [13], prepared from urea and formaldehyde, which then condenses with a suitable primary amine [7,8] or by condensing urea with the previously prepared dimethylol derivative of a primary amine with or without isolation of the indicated intermediate product [9]. The N-methylene derivative of a primary amine [10] may be used in place of the latter. Ethylenediamine and ethanolamine have been used [3][4][5] as bifunctional amines in a three-component condensation and ethanolamine and N,N-dimethylethylenediamine [7] in the condensation with DMU. In all four cases the expected 5-substituted 1,3,5-triazinan-2-one cyclic Mannich bases were obtained.

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