Charge carrier mobility is still the most challenging issue that should be overcome to realize everyday organic electronics in the near future. In this Communication, we show that introducing smart side-chain engineering to polymer semiconductors can facilitate intermolecular electronic communication. Two new polymers, P-29-DPPDBTE and P-29-DPPDTSE, which consist of a highly conductive diketopyrrolopyrrole backbone and an extended branching-position-adjusted side chain, showed unprecedented record high hole mobility of 12 cm(2)/(V·s). From photophysical and structural studies, we found that moving the branching position of the side chain away from the backbone of these polymers resulted in increased intermolecular interactions with extremely short π-π stacking distances, without compromising solubility of the polymers. As a result, high hole mobility could be achieved even in devices fabricated using the polymers at room temperature.

Poly [2,5-bis(2-decyldodecyl)pyrrolo [3,4-c]pyrrole-1,4(2H,5H)-dione-(E)-1,2-di(2,2 0 -bithiophen-5-yl) ethene] (PDPPDBTE) was successfully incorporated as a p-type hole transporting material in solid-state organicinorganic hybrid solar cells. The excellent optical and electrical properties of organo-lead halide perovskite (CH 3 NH 3 PbI 3 ) nanocrystals used as light harvesters yielded a 9.2% power conversion efficiency (PCE) for the best-performing cell that exceeded the value (7.6%) obtained from the best hole conductor yet reported (2,2 0 ,7,7 0 -tetrakis(N,N-di-p-methoxyphenyl-amine)9,9 0 -spirobifluorene, spiro-MeOTAD). The high PCE was attributed to the optimal oxidation potential (5.4 eV) and excellent charge carrier mobility of the polymer. The hydrophobicity of the polymer prevented water permeation into the porous perovskite heterojunction, and long-term aging tests over 1000 hours confirmed the enhanced stability of the PDPPDBTE-based cells. Broader contextSolid-state organic-inorganic hybrid solar cells have been extensively investigated as an alternative promising energy conversion devices to the conventional silicon-based photovoltaics. With the successful demonstration of the solar cells which utilize lead halide perovskite nanocrystals as excellent light harvesters the overall efficiencies rapidly increased during the last year, yielding over 15% of remarkable performance. Further enhancement of the efficiency could be realized by developing new hole transporting materials with high electrical properties and proper oxidation potential with respect to the energy level of perovskite. To this end, the conjugated polymers are thought to be an alternative to small molecular hole conductors since they have unique charge transport properties with tunable oxidation potential. In this work, we report an efficient stable hybrid solar cells incorporating diketopyrrolopyrrole-containing polymers (PDPPDBTE). With an appropriate oxidation potential of 5.4 eV vs. the vacuum level, the PDPPDBTE conjugated polymer is expected to function efficiently as a hole transporting material. Furthermore, the excellent long-term stability of polymer-based solar cells also guarantee their potential applications.

A high-performance naphthalene diimide (NDI)-based conjugated polymer for use as the active layer of n-channel organic fi eld-effect transistors (OFETs) is reported. The solution-processable n-channel polymer is systematically designed and synthesized with an alternating structure of long alkyl substituted-NDI and thienylene-vinylene-thienylene units (PNDI-TVT). The material has a well-controlled molecular structure with an extended π -conjugated backbone, with no increase in the LUMO level, achieving a high mobility and highly ambient stable n-type OFET. The top-gate, bottomcontact device shows remarkably high electron charge-carrier mobility of up to 1.8 cm 2 V − 1 s − 1 ( I on / I off = 10 6 ) with the commonly used polymer dielectric, poly(methyl methacrylate) (PMMA). Moreover, PNDI-TVT OFETs exhibit excellent air and operation stability. Such high device performance is attributed to improved ππ intermolecular interactions owing to the extended π -conjugation, apart from the improved crystallinity and highly interdigitated lamellar structure caused by the extended ππ backbone and long alkyl groups.the morphology of the polymer fi lm, with its mixture of edge-on and face-on orientation, auto-encapsulation effect by the overlaid gate and gate dielectric layer, and low LUMO energy level of the specifi cally designed polymer. ConclusionsWe designed and synthesized a new solution-processable n-channel polymer with an extended π -conjugated backbone, without increasing the LUMO level. The obtained polymer, PNDI-TVT, had a well-controlled alternating structure consisting of a long alkyl chain-substituted NDI as an electron acceptor unit and TVT as a donor unit. The PNDI-TVT copoly mer demonstrated a remarkably high electron-carrier mobility of up to 1.8 cm 2 V − 1 s − 1 ( I on / I off = 10 6 ) and high air and bias stress stability. To the best of our knowledge, this newly developed material showed the highest n-type mobility, in combination with excellent air and operation stabilities, among the reported n-channel conjugated polymers. The superior performance of PNDI-TVT OFET was attributed to improved ππ intermolecular interactions because of the extended π -conjugation, improved crystallinity with a highly interdigitated lamellar structure owing to the extended backbone and long alkyl groups, and mixed face-on and edge-on orientation.

A record-breaking high electron mobility of 7.0 cm(2) V(-1) s(-1) for n-channel polymer OFETs is reported. By the incorporation of only one nitrile group as an electron-withdrawing function in the vinyl linkage of the DPP-based copolymer, a dramatic inversion of majority charge-carriers from holes to electrons is achieved.

The new deep-blue iridium(III) complexes, (TF)2Ir(pic), (TF)2Ir(fptz), (HF)2Ir(pic), and (HF)2Ir(fptz), consisting of 2',4″-difluororphenyl-3-methylpyridine with trifluoromethyl carbonyl or heptafluoropropyl carbonyl at the 3' position as the main ligand and a picolinate or a trifluoromethylated-triazole as the ancillary ligand, were synthesized and characterized for applications in organic light-emitting diodes (OLEDs). Density function theory (DFT) calculations showed that these iridium complexes had a wide band gap, owing to the introduction of the strong electron withdrawing perfluoro carbonyl group. Time-dependent DFT (TD-DFT) calculations suggested that their lowest triplet excited state was dominated by a HOMO → LUMO transition and that the contribution of the metal-to-ligand charge transfer (MLCT) was higher than 34% for all four complexes, indicating that strong spin-orbit coupling exists in the complexes. The 10 wt % (TF)2Ir(pic) doped 9-(3-(9H-carbazole-9-yl)phenyl)-3-(dibromophenylphosphoryl)-9H-carbazole (mCPPO1) film exhibited the highest photoluminescence quantum yield of 74 ± 3% among the films based on the four complexes. Phosphorescent OLEDs based on (TF)2Ir(pic) and (TF)2Ir(fptz) exhibited maximum external quantum efficiencies of 17.1% and 8.4% and Commission Internationale de l'Eclairage (CIE) coordinates of (0.141, 0.158) and (0.147, 0.116), respectively. These CIE coordinates represent some of the deepest blue emissions ever achieved from phosphorescent OLEDs with considerably high EQEs.