Graphene electronic circuits are prepared on paper substrates by using graphene nanoplates and applied to foldable paper-based electronics. The graphene circuits show a small change in conductance under various folding angles and maintain an electronic path on paper substrates after repetition of folding and unfolding. Foldable paper-based applications with graphene circuits exhibit excellent folding stability.

Dual emitting cores for thermally activated delayed fluorescent (TADF) emitters were developed. Relative to the corresponding TADF emitter with a single emitting core the TADF emitter with a dual emitting core, 3,3',5,5'-tetra(carbazol-9-yl)-[1,1'-biphenyl]-2,2',6,6'-tetracarbonitrile, showed enhanced light absorption accompanied by a high photoluminescence quantum yield. The quantum and power efficiencies of the TADF devices were enhanced by the dual emitting cores.

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6786 wileyonlinelibrary.com TADF OLEDs. [16][17][18][19][20] The QE of green and blue TADF OLEDs is as high as 20%, which suggests that the TADF OLEDs have a potential as the high effi ciency solution-processed OLEDs. Our group already reported that the QE of green TADF OLEDs can be improved up to 18.3% by increasing the solubility of the TADF emitters using a t -butyl substituent. [ 21 ] The t -butyl substitution has been widely used as an approach to increase the solubility of organic materials and was successful in the design of soluble green TADF emitters. However, the t -butyl modifi cation is not appropriate in the design of blue TADF emitters because of red shift of emission color due to strong electron donating character of the t -butyl modifi ed carbazole unit. Therefore, a different approach to increase the solubility and to induce blue shift of emission color is necessary in order to develop soluble blue TADF emitters.In this work, two blue TADF emitters, 2,4,6-tri(9H-carbazol-9-yl)-3,5-difl uorobezonitrile (3CzFCN) and 2,3,4,6-tetra(9H-carbazol-9-yl)-5-fl uorobenzeonitrile (4CzFCN), were developed as soluble blue TADF emitters with improved solubility and blue emission color. The F atom was introduced as an electron withdrawing unit instead of CN to meet the requirements of the soluble blue TADF emitters through improved solubility by hydrophobic nature of F and blue emission by relatively weak electron withdrawing nature of the F atom. The F atom has never been adopted in the molecular design of soluble TADF emitters as well as vacuum evaporable TADF emitters. The two blue TADF emitters exhibited good solubility and could be easily coated by spin-coating process. A high QE of 20.0% with a blue emission color was achieved using the 4CzFCN blue TADF emitter by solution process. This is the fi rst work reporting high QE of 20% in the solution-processed blue TADF OLEDs. It was also demonstrated that the soluble blue TADF OLEDs are comparable to vacuum evaporable blue TADF OLEDs and solution-processed blue phosphorescent OLEDs in terms of QE. Results and DiscussionThe soluble blue TADF emitters are required to possess good solubility in solvent, small singlet-triplet energy gap for TADF emission, high photoluminescence (PL) quantum yield, and pure blue emission color. Therefore, electron withdrawing moieties which can increase the solubility of the molecule should be included in the molecular design. We reported that

This review discusses interfacial layers in organic photovoltaic devices. The first part of the review focuses on the hole extraction layer, which is located between a positive electrode and an organic photoactive material. Strategies to improve hole extraction from the photoactive layer include incorporation of several different types of hole extraction layers, such as conductive polymeric materials, self-assembled molecules and metal oxides, as well as surface treatment of the positive electrodes and the conductive polymeric layers. In the second part, we review recent research on interlayers that are located between a negative electrode and a photoactive layer to efficiently extract electrons from the active layer. These materials include titanium oxides, metal fluorides and other organic layers.