Systematic side-chain engineering has been performed for diketopyrrolopyrrole-selenophene vinylene selenophene (DPP-SVS) polymers to determine the optimal side-chain geometries for the most efficient charge transport, and the structure-property relationship has been thoroughly investigated using a range of analyses. A series of DPP-SVS polymers, ranging from 25-DPP-SVS to 32-DPP-SVS, with branched alkyl groups containing linear spacer groups from C2 to C9 has been synthesized, and the electrical performance of these polymers is significantly dependent on both the length of the spacer group and its odd-even characteristics. Spacer groups with even numbers of carbon atoms exhibit chargecarrier mobilities that are one order of magnitude higher than those with odd numbers of carbon atoms. The optimized charge transport has been obtained from 29-DPP-SVS with C6 spacer, showing the maximum mobility of 13.9 cm 2 V −1 s −1 (V GS , V DS = −100 V) and 17.8 cm 2 V −1 s −1 (V GS , V DS = −150 V). Longer spacer groups deviate from the odd-even trend. In addition to the exceptionally high charge-carrier mobilities of the DPP-SVS polymers, the results obtained herein provide new insight into the molecular design of high-performance polymer semiconductors.

enhancing the open-circuit voltage ( V oc ) and extending the absorption range [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] and (ii) superior morphological stability to mechanical and thermal stress, which is a critical requirement for producing fl exible and portable devices. [ 3 ] Despite these defi nite advantages, the power conversion effi ciencies (PCEs) in most of the all-PSCs systems are behind their fullerene counterparts, and only a few systems exhibited PCE values above 6%. [1][2][3][4][5][6][7][8][9] Their PCEs were usually limited by low short-circuit current density ( J sc ) and fi ll factor (FF), which were mainly caused by (i) largescale phase separation due to energetically favored polymer-polymer demixing, [ 3,15 ] (ii) lower electron mobility of polymer acceptors than fullerenes, [ 21 ] and (iii) ineffi cient charge dissociation at the donor/ acceptor (D/A) interface due to dominant geminate recombination process. [ 20,22 ] For the polymer/fullerene PSCs, the isotropic molecular structures of spherical-shaped fullerene-based acceptors produced efficient electron transport in the 3D directions. [ 23,24 ] In contrast, because both D and A polymers in all-PSC systems have highly anisotropic conjugated structure, the charge transport in polymer thin fi lm is determined by their specifi c molecular orientations. [ 18,[24][25][26][27][28][29][30][31][32] For example, the polymer acceptors with strong face-on geometry relative to the electrodes are highly benefi cial for facilitating the electron transport in the solar cell devices. [ 18,[29][30][31][32] Also, the charge dissociation effi ciencies are strongly dependent on the molecular orientations of the D and A polymers relative to the D/A interface, because the distance between the π-orbitals of the D and A polymers should be reduced to overcome the Coulombic binding energy of the excitons and facilitate the charge separation. [ 20,24,29,[32][33][34][35][36] For example, the strong π-orbital overlap by face-to-face stacking between D and A polymer chains is crucial for generating free charges, while misoriented D and A polymer chains inescapably caused geminate recombination at the interface. [ 20,32 ] Therefore, controlling the molecular orientation of conjugated polymers along with strong crystalline behaviors is very important for enhancing both the charge transport in thin fi lm and the charge dissociation at the D/A interface, thereby optimizing the performances of all-PSCs. PSCs), but is often diffi cult to rationally control. Here, an effective approach for tuning the molecular crystallinity and orientation of naphthalenediimide-bithiophene-based n-type polymers (P(NDI2HD-T2)) by controlling their number average molecular weights ( M n ) is reported. A series of P(NDI2HD-T2) polymers with different M n of 13.6 ( P L ), 22.9 ( P M ), and 49.9 kg mol −1 ( P H ) are prepared by changing the amount of end-capping agent (2-bromothiophene) during polymerization. Increasing the M n values of P(NDI2HD-T2) polymers leads to...

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The directed assembly of block copolymer nanostructures with large periods exceeding 100 nm remains challenging because the translational ordering of long-chained block copolymer is hindered by its very low chain mobility. Using a solvent-vapor annealing process with a neutral solvent, which was sequentially combined with a thermal annealing process, we demonstrate the rapid evolution of a perpendicularly oriented lamellar morphology in high molecular weight block copolymer films on neutral substrate. The synergy with the topographically patterned substrate facilitated unidirectionally structural development of ultrahigh molecular weight block copolymer thin films-even for the structures with a large period of 200 nm-leading to perfectly guided, parallel, and highly ordered line-arrays of perpendicularly oriented lamellae in the trenched confinement. This breakthrough strategy, which is applicable to nanolithographic pattern transfer to target substrates, can be a simple and efficient route to satisfy the demand for block copolymer assemblies with larger feature sizes on hundreds of nanometers scale.

Nanoporous structures were obtained by the self-assembly of polystyrene-b-poly(methyl methacrylate) (PS-b-PMMA) block copolymers (BCP) where, in thick films, cylindrical microdomains were oriented normal to the substrate and air interfaces, and in the interior of the films, the microdomains were randomly oriented. Continuous nanopores that penetrated through the film were readily produced by a simple preferential swelling of the PMMA microdomains. The confined swelling and rapid contraction of PMMA microdomains generated well-defined uniform pores with diameters to 17.5 nm. The size selectivity and rejection of Au nanoparticles (NPs) for these ultrafiltration (UF) membranes were demonstrated, suggesting an efficient route to tunable, noncomponent-degradative UF membranes.