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1,3-Dimethyl-2,3-dihydrobenzo[d]imidazoles,1H, and 1,1',3,3'-tetramethyl-2,2',3,3'-tetrahydro-2,2'-bibenzo[d]imidazoles,1₂, are of interest as n-dopants for organic electron-transport materials. Salts of 2-(4-(dimethylamino)phenyl)-4,7-dimethoxy-, 2-cyclohexyl-4,7-dimethoxy-, and 2-(5-(dimethylamino)thiophen-2-yl)benzo[d]imidazolium (1g–i⁺, respectively) have been synthesized and reduced with NaBH₄to1gH,1hH, and1iH, and with Na:Hg to1g₂and1h₂. Their electrochemistry and reactivity were compared to those derived from 2-(4-(dimethylamino)phenyl)- (1b⁺) and 2-cyclohexylbenzo[d]imidazolium (1e⁺) salts.E(1⁺/1^•) values for 2-aryl species are less reducing than for 2-alkyl analogues, i.e., the radicals are stabilized more by aryl groups than the cations, while 4,7-dimethoxy substitution leads to more reducingE(1⁺/1^•) values, as well as cathodic shifts inE(1₂^•+/1₂) andE(1H^•+/1H) values. Both the use of 3,4-dimethoxy and 2-aryl substituents accelerates the reaction of the1Hspecies with PC₆₁BM. Because 2-aryl groups stabilize radicals,1b₂and1g₂exhibit weaker bonds than1e₂and1h₂and thus react with 6,13-bis(triisopropylsilylethynyl)pentacene (VII) via a “cleavage-first” pathway, while1e₂and1h₂react only via “electron-transfer-first”.1h₂exhibits the most cathodicE(1₂^•+/1₂) value of the dimers considered here and, therefore, reacts more rapidly than any of the other dimers withVIIvia “electron-transfer-first”. Crystal structures show rather long central C–C bonds for1b₂(1.5899(11) and 1.6194(8) Å) and1h₂(1.6299(13) Å). 

Molecular doping can increase the conductivity of organic semiconductors and plays an increasingly important role in emerging and established plastic electronics applications. 4-(1,3-Dimethyl-2,3-dihydro-1 H -benzimidazol-2-yl)- N , N -dimethylaniline (N-DMBI-H) and tris(pentafluorophenyl)borane (BCF) are established n- and p-dopants, respectively, but neither functions as a simple one-electron redox agent. Molecular hydrogen has been suggested to be a byproduct in several proposed mechanisms for doping using both N-DMBI-H and BCF. In this paper we show for the first time the direct detection of molecular hydrogen in the uncatalysed doping of a variety of polymeric and molecular semiconductors using these dopants. Our results provide insight into the doping mechanism, providing information complementary to that obtained from more commonly applied methods such as optical, electron spin resonance, and electrical measurements. 

The effects of sequential n-doping on a high-electron-mobility naphthalene-diimide-based copolymer poly[( N , N ′-bis(2-decyltetradecyl)-naphthalene-1,8:4,5-bis(dicarboximide)-2,6-diyl)-(selenophene-2,5-diyl)-(benzo[ c ][1,2,5]thiadiazole-4,7-diyl)-(selenophene-2,5-diyl)], PNBS, are reported. Grazing-incidence XRD measurements show that PNBS doped with 2,2′-bis(4-(dimethylamino)phenyl)-1,1′,3,3′-tetramethyl-2,2′,3,3′-tetrahydro-1 H ,1′ H -2,2′-bibenzo[ d ]imidazole, (N-DMBI) 2 , has increased order relative to both the pristine polymer and a film doped with ruthenium pentamethylcyclopentadienyl mesitylene dimer. Films of PNBS optimally doped with (N-DMBI) 2 show electrical conductivities approaching 2 mS cm −1 in air. Temperature-dependent electrical measurements suggest that the polaronic charge carriers are highly localized, which is consistent with the moderate conductivity values obtained. 

Abstract While metal‐halide perovskite light‐emitting diodes (PeLEDs) hold the potential for a new generation of display and lighting technology, their slow operation speed and response time limit their application scope. Here, high‐speed PeLEDs driven by nanosecond electrical pulses with a rise time of 1.2 ns are reported with a maximum radiance of approximately 480 kW sr⁻¹ m⁻²at 8.3 kA cm⁻², and an external quantum efficiency (EQE) of 1% at approximately 10 kA cm⁻², through improved device configuration designs and material considerations. Enabled by the fast operation of PeLEDs, the temporal response provides access to transient charge carrier dynamics under electrical excitation, revealing several new electroluminescence quenching pathways. Finally, integrated distributed feedback (DFB) gratings are explored, which facilitate more directional light emission with a maximum radiance of approximately 1200 kW sr⁻¹m⁻²at 8.5 kA cm⁻², a more than two‐fold enhancement to forward radiation output.