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Developing polymers with high electrical conductivity (σ) after n‐doping is a great challenge for the advance of the field of organic thermoelectrics (OTEs). Herein, we report a series of thiazole imide‐based n‐type polymers by gradually increasing selenophene content in polymeric backbone. Thanks to the strong intramolecular noncovalent N⋅⋅⋅S interaction and enhanced intermolecular Se⋅⋅⋅Se interaction, with the increase of selenophene content, the polymers show gradually lowered LUMOs, more planar backbone, and improved film crystallinity versus the selenophene‐free analogue. Consequently, polymer PDTzSI−Se with the highest selenophene content achieves a champion σ of 164.0 S cm−1 and a power factor of 49.0 μW m−1 K−2 in the series when applied in OTEs after n‐doping. The σ value is the highest one for n‐type donor‐acceptor OTE materials reported to date. Our work indicates that selenophene substitution is a powerful strategy for developing high‐performance n‐type OTE materials and selenophene incorporated thiazole imides offer an excellent platform in enabling n‐type polymers with high backbone coplanarity, deep‐lying LUMO and enhanced mobility/conductivity. [ABSTRACT FROM AUTHOR]

Designing n‐type polymers with high electrical conductivity remains a major challenge for organic thermoelectrics (OTEs). Herein, by devising a novel selenophene‐based electron‐deficient building block, the pronounced advantages of selenium substitution in simultaneously enabling advanced n‐type polymers is demonstrated with high mobility (≈2 orders of magnitude higher versus their sulfur‐based analogues due to both intensified intra‐ and inter‐chain interactions) and much improved n‐doping efficiency (enabled by the largely lowered LUMO level with a ≈0.2 eV margin) of the resulting polymers. Via side chain optimization and donor engineering, the selenium‐substituted polymer, f‐BSeI2TEG‐FT, achieves a highest conductivity of 103.5 S cm−1 and power factor of 70.1 µW m−1 K−2, which are among the highest values reported in literature for n‐type polymers, and f‐BSeI2TEG‐FT greatly outperformed the sulfur‐based analogue polymer by 40% conductivity increase. These results demonstrate that selenium substitution is a very effective strategy for improving n‐type performance and provide important structure‐property correlations for developing high‐performing n‐type OTE materials. [ABSTRACT FROM AUTHOR]

n‐Type semiconducting polymers with high thermoelectric performance remain challenging due to the scarcity of molecular design strategy, limiting their applications in organic thermoelectric (OTE) devices. Herein, we provide a new approach to enhance the OTE performance of n‐doped polymers by introducing acceptor‐acceptor (A‐A) type backbone bearing branched ethylene glycol (EG) side chains. When doped with 4‐(2,3‐dihydro‐1,3‐dimethyl‐1H‐benzimidazol‐2‐yl)‐N,N‐dimethylbenzenamine (N‐DMBI), the A‐A homopolymer PDTzTI‐TEG exhibits n‐type electrical conductivity (σ) up to 34 S cm−1 and power factor value of 15.7 μW m−1 K−2. The OTE performance of PDTzTI‐TEG is far greater than that of homopolymer PBTI‐TEG (σ=0.27 S cm−1), indicating that introducing electron‐deficient thiazole units in the backbone further improves the n‐doping efficiency. These results demonstrate that developing A‐A type polymers with EG side chains is an effective strategy to enhance n‐type OTE performance. [ABSTRACT FROM AUTHOR]

Dopant‐free hole‐transporting layers (HTLs) are highly desired for realizing efficient and stable perovskite solar cells (PVSCs), but only very few of them can enable power conversion efficiencies (PCEs) over 20%. Herein, two imide‐functionalized triarylamine‐based donor‐acceptor (D‐A) type copolymers, PBTI‐TPA and PTTI‐TPA, are developed and applied as dopant‐free HTLs in inverted PVSCs. The combination of a classic redox‐active triphenylamine donor unit and an electron‐withdrawing oligothiophene imide co‐unit with rigid and planar backbone furnishes the two polymers with quasi‐planar backbone, suitable frontier molecular orbital (FMO) energy levels, favorable thermal stability, appropriate film morphology, and passivation effect. More importantly, the greatly improved hole mobility renders them as promising HTLs for PVSCs. As a result, the undoped PTTI‐TPA‐based inverted PVSCs deliver a remarkable PCE up to 21% as well as negligible hysteresis and substantial long‐term stability, outperforming the devices based on PBTI‐TPA and PTAA. The performance also represents one of the highest PCEs reported to date for PVSCs based on dopant‐free polymeric HTLs. The results highlight the great potentials of oligothiophene imides for constructing donor‐acceptor polymeric HTLs for enabling high‐performance dopant‐free PVSCs. [ABSTRACT FROM AUTHOR]

High‐performance nonfullerene ternary organic solar cells (OSCs) with two polymer donors are less frequently reported because of the limited numbers of efficient polymer donors with good compatibility. Herein, a wide‐bandgap polymer P1 with a deep‐lying highest occupied molecular orbital (HOMO) level is incorporated as the third component into the benchmark PM6:Y6 binary system to fabricate ternary OSCs. The introduction of P1 not only leads to extended absorption coverage and forms a cascade‐like energy level alignment but also shows excellent compatibility with PM6, resulting in a favorable morphology in the ternary blend. More importantly, P1 possesses a deeper HOMO level (−5.6 eV) than most well‐known donor polymers, which enables resulting ternary OSCs with an improved open‐circuit voltage. As a result, the optimized ternary OSCs with 40 wt% P1 in donors achieve a power conversion efficiency (PCE) of 16.2% with a small nonradiative recombination loss of 0.23 eV, which is among the highest values of ternary OSCs based on two polymer donors. In addition, the ternary OSCs show a broad composition tolerance with a high PCE of over 14% throughout the whole blend ratios. These results provide an effective approach to fabricate efficient ternary OSCs by synergizing two wide‐bandgap polymer donors. [ABSTRACT FROM AUTHOR]