New π-conjugated polymers with strong electron affinity, PNDTI-BBTs, consisting of naphtho­[2,3-b:6,7-b′]­dithiophenediimide (NDTI) and benzo­[1,2-c:4,5-c′]­bis­[1,2,5]­thiadiazole (BBT) units, were synthesized. PNDTI-BBTs have low-lying LUMO energy levels (∼−4.4 eV), which is sufficiently low for air-stable electron transport in organic field-effect transistors and for being readily doped by a well-known n-dopant, N,N-dimethyl-2-phenyl-2,3-dihydro-1H-benzoimidazole (N-DMBI), affording doped polymer films with relatively high conductivities and Seebeck coefficients. Depending on the solubilizing alkyl groups (2-decyltetradecyl, PNDTI-BBT-DT, or 3-decylpentadecyl groups, PNDTI-BBT-DP), not only the electron mobility in the transistor devices with the pristine polymer thin films (PNDTI-BBT-DT: ∼0.096 cm2 V–1 s–1; PNDTI-BBT-DP: ∼0.31 cm2 V–1 s–1) but also the conductivity and power factor of the doped thins films (PNDTI-BBT-DT: ∼0.18 S cm–1 and ∼0.6 μW m–1 K–2; PNDTI-BBT-DP: ∼5.0 S cm–1 and ∼14 μW m–1 K–2) were drastically changed. The differences in the electric properties were primarily ascribed to the better crystalline nature of the PNDTI-BBT-DP than those of PNDTI-BBT-DT in the thin-film state. Furthermore, UV–vis and ESR spectra demonstrated that doping effectiveness was largely affected by the alkyl groups: the PNDTI-BBT-DP films with better crystalline order prevented overdoping, resulting in ca. 20 times higher conductivity and power factors. From these results, it can be concluded that tuning the intermolecular interaction and consequently obtaining the thin-film with well-ordered polymers by the alkyl side chains is a promising strategy for developing superior thermoelectric materials.

of intramolecular vibrational relaxation and the nonradiative rate (k q (RT)) of triplet quenching due to interactions with ambient surrounding are much larger than k p . Therefore, reports of RTP from metal-free aromatic molecules in ambient condition have been scarce. [8,9] However, in the past 5 years, RTP from metal-free aromatics under ambient conditions has been successfully realized by suppressing k nr (RT) + k q (RT) in various materials, such as host-guest systems, carbon nanodots, and aromatic crystals. [10][11][12][13][14][15][16] In some of these materials, ultralong-lived RTP (persistent RTP) has sufficient intensity and lifetime in air for an observation by naked eye after ceasing the irradiation. [12][13][14][15][16] Due to its ultralong lifetime at RT on the order of seconds, the detection of persistent RTP is not affected by autofluorescence or scattering of the excitation light, [17] and as such can be measured experimentally with low-cost detectors, thus fulfilling one of the requirements for application in bioimaging, optical sensing, and security. [18][19][20][21] For the appearance of persistent RTP under ambient conditions, high efficiency of intersystem crossing (ISC) from the lowest singlet excited state (S 1 ) to the lowest triplet excited state (T 1 ) and suppression of k nr (RT) + k q (RT) are crucial. Efficient ISC from S 1 to T 1 can be obtained by molecular design based on symmetry rules or the El-Sayed rule. [22][23][24] Therefore, the elucidation of the mechanism of suppression of k nr (RT) + k q (RT) is very important factor for persistent RTP. Some heavy atomfree conjugated molecules dispersed in polymers show weak persistent RTP under inert conditions because of the potential suppression of k nr (RT) + k q (RT). [25][26][27][28] However, the analysis of the mechanism of k nr (RT) and k q (RT) suppression was complicated because the experimental separation of the k nr (RT) component from k nr (RT) + k q (RT) was inconclusive. [29] On the other hand, in the case of host-guest systems, the separation of the two nonradiative processes k nr (RT) and k q (RT) was realized by introducing very rigid host matrix with high T 1 energy. The rigid matrix can suppress thermally activated energy transfer over large energy difference from guest molecules to the host and protect from oxygen, resulting in large decrease k nr (RT) + k q (RT) and leading to efficient persistent RTP under ambient conditions. [12] Later, experiments in such rigid hosts revealed that k nr (RT) and k p were intrinsically comparable, [24] Persistent room-temperature phosphorescence (RTP) under ambient conditions is attracting attention due to its strong potential for applications in bioimaging, sensing, or optical recording. Molecular packing leading to a rigid crystalline structure that minimizes nonradiative pathways from triplet state is often investigated for efficient RTP. However, for complex conjugated systems a key strategy to suppress the nonradiative deactivation is not found yet. Here, the origin of small ra...

On the basis of an excellent transistor material, [1]benzothieno[3,2-b][1]benzothiophene (BTBT), a series of highly conductive organic metals with the composition of (BTBT)2XF6 (X = P, As, Sb, and Ta) are prepared and the structural and physical properties are investigated. The room-temperature conductivity amounts to 4100 S cm(-1) in the AsF6 salt, corresponding to the drift mobility of 16 cm(2) V(-1) s(-1). Owing to the high conductivity, this salt shows a thermoelectric power factor of 55-88 μW K(-2) m(-1), which is a large value when this compound is regarded as an organic thermoelectric material. The thermoelectric power and the reflectance spectrum indicate a large bandwidth of 1.4 eV. These salts exhibit an abrupt resistivity jump under 200 K, which turns to an insulating state below 60 K. The paramagnetic spin susceptibility, and the Raman and the IR spectra suggest 4kF charge-density waves as an origin of the low-temperature insulating state.

A 1 : 1 metallic charge-transfer salt is obtained by cosublimation of (Z,E)-(SMe)2Me2TTF and TCNQ.