A soluble precursor of dinaphtho[2,3-b:2',3'-f]thieno[3,2-b]thiophene (DNTT) is developed for high-performance printed organic thin-film transistors (OTFTs). The DNTT precursor enables excellent thin-film formation and can induce specific phase separations when blended with inert polymers. The DNTT OTFTs processed from the precursor/polymer blend exhibit field-effect mobilities of up to 1.1 cm(2) V(-1) s(-1) and excellent durability against air exposure and thermal stress.

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Using steady-state and time-resolved photoluminescence (PL) spectroscopy, we have investigated the temperature dependence of PL properties of 1,2,3,5-tetrakis(carbazol-9-yl)-4,6-dicyano-benzene (4CzIPN), which have a small energy gap between its singlet and triplet excited states and thus exhibits efficient thermally activated delayed fluorescence [H. Uoyama et al., Nature 492, 235 (2012)]. Below around 100 K, PL quantum efficiency of 4CzIPN thin films is largely suppressed and strong photoexcitation intensity dependence appears. These features can be explained by using rate equations for the densities of singlet and triplet excited states considering a triplet-triplet annihilation process.

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