Two narrow‐bandgap block conjugated polymers with a (D1–A1)–(D2–A2) backbone architecture, namely PBDB‐T‐b‐PIDIC2T and PBDB‐T‐b‐PTY6, are designed and synthesized for single‐component organic solar cells (SCOSCs). Both polymers contain same donor polymer, PBDB‐T, but different polymerized nonfullerene molecule acceptors. Compared to all previously reported materials for SCOSCs, PBDB‐T‐b‐PIDIC2T and PBDB‐T‐b‐PTY6 exhibit narrower bandgap for better light harvesting. When incorporated into SCOSCs, the short‐circuit current density (Jsc) is significantly improved to over 15 mA cm−2, together with a record‐high power conversion efficiency (PCE) of 8.64%. Moreover, these block copolymers exhibit low energy loss due to high charge transfer (CT) states (Ect) plus small non‐radiative loss (0.26 eV), and improved stability under both ambient condition and continuous 80 °C thermal stresses for over 1000 h. Determination of the charge carrier dynamics and film morphology in these SCOSCs reveals increased carrier recombination, relative to binary bulk‐heterojunction devices, which is mainly due to reduced ordering of both donor and acceptor fragments. The close structural relationship between block polymers and their binary counterparts also provides an excellent framework to explore further molecular features that impact the photovoltaic performance and boost the state‐of‐the‐art efficiency of SCOSCs.

Fluorine (F) and chlorine (Cl) substitution in organic semiconductors has been found to be effective for enhancing the performance of organic photovoltaics. However, the effect of these substitutions on charge transport properties of organic semiconductors remains elusive. A series of naphthalene diamide (NDI)‐based copolymers: N2200, the corresponding fluorinated N2200 (F‐N2200), and chlorinated N2200 (Cl‐N2200) are employed to fabricate field‐effect transistors. Gate‐dependent and temperature‐dependent mobility are measured and analyzed to reveal the intrinsic electronic properties of the polymers. It is found that F substitution decreases energetic disorder of the semiconductor while Cl substitution increases it. These findings are further supported by density functional theory calculations and characterizations on the performance of doped devices based on the three polymers. Overall, the influence of fluorination and chlorination on charge transport in those NDI‐based polymers is identified and clarified, which is important for justifying the wide employment of fluorination and chlorination strategies in organic electronics.

Doping is a powerful technique for tuning the electrical properties of organic semiconductors (OSCs). Although numerous studies are performed on OSC doping, thus far only a few n-type dopants have been developed. Herein, two low-cost nucleophilic organic bases are reported, namely 1,5,7-Triazabicyclo [4.4.0] dec-5-ene (TBD) and 1,5-Diazabicyclo [4.3.0] non-5-ene (DBN) for n-doping of OSCs. The two dopants are found to significantly enhance the electrical conductivity of OSCs. In particular, compared to the classic n-dopant 4-(2,3-Dihydro-1,3-dimethyl-1H-benzimidazol-2-yl)-N, N-dimethylbenzylamine (N-DMBI), DBN results in significantly higher conductivity and also lower activation energy in N2200 films, indicating its high doping performance. The utilization of the n-dopants for improving device performance and controlling the device polarity of organic field-effect transistors are demonstrated.Furthermore, these dopants are employed for fabricating organic thermoelectric devices, and the power factor value of DBN-doped N2200 films is found to be about 1.6 times higher than that of N-DMBI-doped films. These results show the feasibility of using low-cost organic bases as efficient n-dopants and demonstrate their promising applications in organic electronics.

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Abstract:In this paper; an imidazolium ionic liquid (IL) is used to functionalize multi-walled carbon nanotubes (MWNTs) by covalent bonding on the MWNT surface. The functionalization not only provides a hydrophilic surface for ion accessibility but also prevents the aggregation of MWNTs. The IL-functionalized MWNTs were then applied for the electrochemical determination of the dihydroxybenzene isomers hydroquinone (HQ); catechol (CC); and resorcinol (RC), exhibiting excellent recognition ability towards the three compounds. The linear calibration ranges for HQ; CC and RC are 0.9-150 µM; 0.9-150 µM and 1.9-145 µM and the detection limits are found to be 0.15 µM for HQ; 0.10 µM for CC and 0.38 µM for RC based on S/N of 3. The proposed electrochemical sensor was also found to be useful for the determination of the dihydroxybenzene isomers in Yellow River water with reliable recovery.