A new strategy of platinum(II) complexation is developed to regulate the crystallinity and molecular packing of polynitrogen heterocyclic polymers, optimize the morphology of the active blends, and improve the efficiency of the resulting nonfullerene polymer solar cells (NF‐PSCs). The newly designed s‐tetrazine (s‐TZ)‐containing copolymer of PSFTZ (4,8‐bis(5‐((2‐butyloctyl)thio)‐4‐fluorothiophen‐2‐yl)benzo[1,2‐b:4,5‐b′]dithiophene‐alt‐3,6‐bis(4‐octylthiophen‐2‐yl)‐1,2,4,5‐tetrazine) has a strong aggregation property, which results in serious phase separation and large domains when blending with Y6 ((2,2′‐((2Z,2′Z)‐((12,13‐bis(2‐ethylhexyl)‐3,9‐diundecyl‐12,13‐dihydro‐[1,2,5]thiadiazolo[3,4‐e]thieno[2″,3″:4′,5′]thieno[2′,3′:4,5]pyrrolo[3,2‐g]thieno[2′,3′:4,5]thieno[3,2‐b]indole‐2,10‐diyl)bis(methanylylidene))bis(5,6‐difluoro‐3‐oxo‐2,3‐dihydro‐1H‐indene‐2,1‐diylidene))dimalononitrile)), and produces a power‐conversion efficiency (PCE) of 13.03%. By adding small amount of Pt(Ph)2(DMSO)2 (Ph, phenyl and DMSO, dimethyl sulfoxide), platinum(II) complexation would occur between Pt(Ph)2(DMSO)2 and PSFTZ. The bulky benzene ring on the platinum(II) complex increases the steric hindrance along the polymer main chain, inhibits the polymer aggregation strength, regulates the phase separation, optimizes the morphology, and thus improves the efficiency to 16.35% in the resulting devices. 16.35% is the highest efficiency for single‐junction PSCs reported so far.

Both fluorine and ester substituted monothiophene yielded a novel thiophene derivative FE-T. The resulting polymer donor S1 enabled single-junction non-fullerene solar cell with over 16% efficiency.

We demonstrated the synthesis and characterization of two conjugated copolymers, PBDTFBZO and PBDTFBZS, consisting of dialkylthiol substituted benzo[1,2-b:4,5-b']dithiophene donor and monofluorinated benzotriazole acceptor blocks. The resulting copolymers show large band gaps, deep HOMO and LUMO energy levels. Improved V(oc), J(sc), and FF were obtained at the same time to increase overall efficiencies of their single and tandem polymer solar cells. The enhanced V(oc) can be ascribed to a low-lying HOMO energy level by incorporating dialkylthiol and fluorine substituents on the polymer backbone. The improvement in J(sc) and FF are likely due to high carrier mobility, suppressed charge recombination, and fine nanostructure morphology. A 7.74% PCE was achieved from the regular single device based on PBDTFBZS:PC71BM blend film with 3% 1,8-diiodooctane (DIO) additive. In combination with low band gap diketopyrrolopyrrole (DPP)-based copolymer, tandem devices based on PBDTFBZS exhibited high PCE up to 9.40%. The results indicate that PBDTFBZO and PBDTFBZS are promising polymer donor materials for future application of large-area polymer solar cells.

Chemical doping is a key process for investigating charge transport in organic semiconductors and improving certain (opto)electronic devices 1-9 . N-(electron)doping is fundamentally more challenging than p-(hole)doping and typically achieves very low doping efficiency (η) <10% 1,10 . An efficient molecular n-dopant should simultaneously exhibit a high reducing power and air stability for broad applicability 1,5,6,9,11 , which is very challenging. Here we show a general concept of catalysed n-doping of organic semiconductors using air-stable precursor-type molecular dopants. Incorporation of a transition metal as vapor-deposited nanoparticles (e.g. Pt, Au, Pd) or solution-processable 2 organometallic complexes (e.g. Pd 2 (dba) 3 ) catalyses the reaction, as assessed by experimental and theoretical evidence, enabling drastically increased η in a much shorter doping time and high electrical conductivities >100 S cm −1 12 . This methodology has technological implications for realizing improved semiconductor devices and offers a broad exploration space of ternary systems comprising catalysts, molecular dopants, and semiconductors, thus opening new opportunities in n-doping research and applications.N-doping of organic semiconductors is important for developing light-emitting diodes 1,6-9 , solar cells 7,8 , thin-film transistors 10 , and thermoelectric devices 12,13 . Although solution-based ndoping is widely investigated, only few air-stable n-dopants have been developed (Fig. S1), with the most prominent being organic hydrides 5,9,14-18 such as benzoimidazole derivatives, dimers of organic radicals 11,19,20 such as nineteen-electron organometallic sandwich compounds, and mono-/multi-valent anions 8,21,22 such as OH − , F − and Ox 2− . These air-stable dopants have a deep ionization potential (IP) in their initial forms, thus, cannot directly transfer electrons to n-dope organic semiconductors with a low electron affinity (EA). For anions, it was shown that dispersion into small anhydrous clusters enables sufficiently high donor levels for n-doping organic semiconductors with EAs up to 2.4 eV 8 . Hydride and dimer dopant precursors (or referred as precursor-type dopants) most undergo a C-H and C-C bond cleavage reaction, respectively, to generate active-doping-species in situ before electron transfer can occur [23][24][25][26] . Thus, their reducing strength and reaction kinetics are strongly affected by the thermodynamics and the activation energies of the doping reaction [23][24][25][26] . If the activation energy to the product is reduced, it is expected that the reaction rate, and extent of doping, will greatly increase (Fig. 1a). 3Transition metal (TM) catalysed C-H and C-C bond cleavage reactions are widely used in organic synthesis, with the most common TMs belonging to group 8-11 elements and the catalysts in the form of nanoparticles (NPs) and organometallic complexes 27,28 . Nanoparticle size, supporting material, and chemical structure of the complex can greatly affect catalytic activities. Thus, an i...

Naphtho[1,2-c:5,6-c']bis[1,2,5]thiadiazole-based small molecules have been synthesized for organic solar cells. The optimized devices processed by a halogen-free solvent of CS2 exhibited a PCE of 11.53% with a small energy loss of 0.57 eV.

n-Type polymers with deep-positioned lowest unoccupied molecular orbital (LUMO) energy levels are essential for enabling n-type organic thin-film transistors (OTFTs) with high stability and n-type organic thermoelectrics (OTEs) with high doping efficiency and promising thermoelectric performance. Bithiophene imide (BTI) and its derivatives have been demonstrated as promising acceptor units for constructing high-performance n-type polymers. However, the electron-rich thiophene moiety in BTI leads to elevated LUMOs for the resultant polymers and hence limits their n-type performance and intrinsic stability. Herein, we addressed this issue by introducing strong electron-withdrawing cyano functionality on BTI and its derivatives. We have successfully overcome the synthetic challenges and developed a series of novel acceptor building blocks, CNI, CNTI, and CNDTI, which show substantially higher electron deficiencies than does BTI. On the basis of these novel building blocks, acceptor–acceptor type homopolymers and copolymers were successfully synthesized and featured greatly suppressed LUMOs (−3.64 to −4.11 eV) versus that (−3.48 eV) of the control polymer PBTI. Their deep-positioned LUMOs resulted in improved stability in OTFTs and more efficient n-doping in OTEs for the corresponding polymers with a highest electrical conductivity of 23.3 S cm–1 and a power factor of ∼10 μW m–1 K–2. The conductivity and power factor are among the highest values reported for solution-processed molecularly n-doped polymers. The new CNI, CNTI, and CNDTI offer a remarkable platform for constructing n-type polymers, and this study demonstrates that cyano-functionalization of BTI is a very effective strategy for developing polymers with deep-lying LUMOs for high-performance n-type organic electronic devices.

Unpaired electrons of organic radicals can offer high electrical conductivity without doping, but they typically suffer from low stability. Herein, we report two organic diradicaloids based on quinoidal oligothiophene derivative (QOT), that is, BTICN and QTICN, with high stability and conductivity by employing imide-bridged fused molecular frameworks. The attachment of a strong electron-withdrawing imide group to the tetracyano-capped QOT backbones enables extremely deeply aligned LUMO levels (from −4.58 to −4.69 eV), cross-conjugated diradical characters, and remarkable ambient stabilities of the diradicaloids with half-lives > 60 days, which are among the highest for QOT diradicals and also the widely explored polyaromatic hydrocarbon (PAH)-based diradicals. Specifically, QTICN based on a tetrathiophene imide exhibits a cross-conjugation assisted self-doping in the film state as revealed by XPS and Raman studies. This property in combination with its ordered packing yields a high electrical conductivity of 0.34 S cm −1 for the QTICN films with substantial ambient stability, which is also among the highest values in organic radical-based undoped conductive materials reported to date. When used as an n-type thermoelectric material, QTICN shows a promising power factor of 1.52 uW m −1 K −2 . Our results not only provide new insights into the electron conduction mechanism of the self-doped QOT diradicaloids but also demonstrate the great potential of fused quinoidal oligothiophene imides in developing stable diradicals and high-performance doping-free n-type conductive materials.

The development of n-type organic electrochemical transistors (OECTs) lags far behind their p-type counterparts. In order to address this dilemma, we report here two new fused bithiophene imide dimer (f-BTI2)-based n-type polymers with abranched methyl end-capped glycol side chain, which exhibit good solubility,l ow-lying LUMO energy levels,f avorable polymer chain orientation, and efficient ion transport property, thus yielding aremarkable OECT electron mobility (m e )ofup to % 10 À2 cm 2 V À1 s À1 and volumetric capacitance (C*) as high as 443 Fcm À3 ,simultaneously.Asaresult, the f-BTI2TEG-FTbased OECTs deliver ar ecord-high maximum geometrynormalized transconductance of 4.60 Scm À1 and am aximum mC* product of 15.2 Fcm À1 V À1 s À1 .T he mC* figure of merit is more than one order of magnitude higher than that of the stateof-the-art n-type OECTs.T he emergence of f-BTI2TEG-FT brings an ew paradigm for developing high-performance ntype polymers for low-power OECT applications.