Organic pi-conjugated polymers are deemed to be soft materials with strong electron-phonon coupling, which results in the formation of polarons, i.e., charge carriers dressed by self-localized distortion of the nuclei. Universal signatures for polarons are optical resonances below the band gap and intense vibrational modes (IVMs), both found in the infrared (IR) spectral region. Here, we study p-doped conjugated homo-and copolymers by combining first-principles modelling and optical spectroscopy from the far-IR to the visible. Polaronic IVMs are found to feature absorption intensities comparable to purely electronic transitions and, most remarkably, show only loose resemblance to the Raman or IR-active modes of the neutral polymer. The IVM frequency is dramatically scaled down (up to 50%) compared to the backbone carbon-stretching modes in the pristine polymers. The very large intensity of IVMs is associated with displacement of the excess positive charge along the backbone driven by specific vibrational modes. We propose a quantitative picture for the identification of these polaron shifting modes that solely based on structural information, directly correlates with their IR intensity. This finding finally discloses the elusive microscopic mechanism behind the huge IR intensity of IVMs in doped polymeric semiconductors.

Noncovalent functionalization of single‐walled carbon nanotubes (SWNTs) using π‐conjugated polymers has become one of the most effective techniques to select semiconducting SWNTs (s‐SWNTs). Several conjugated polymers are used, but their ability to sort metallic and semiconducting species, as well as the dispersions yields, varies as a function of their chemical structure. Here, three polymers are compared, namely, poly[2,6‐(4,4‐bis‐(2‐dodecyl)‐4H‐cyclopenta[2,1‐b;3,4b′]dithiophene)‐alt‐4,7(2,1,3‐benzothiadiazole)] (P12CPDTBT), poly(9,9‐di‐n‐dodecylfluorenyl‐2,7‐diyl) (PF12), and poly(3‐dodecylthiophene‐2,5‐diyl) (P3DDT) in their ability to select two types of carbon nanotubes comprising small (≈1 nm) and large (≈1.5 nm) diameters. P12CPDTBT is a better dispersant than PF12 for small diameter nanotubes, while both polymers are good dispersants of large diameter nanotubes. However, these dispersions contain metallic species. P3DDT, instead presents the best overall performance regarding the selectivity toward semiconducting species, with a dispersion yield for s‐SWNTs of 15% for small and 21% for large diameter nanotubes. These results are rationalized in terms of electronic and chemical structure showing that: (i) the binding energy is stronger when more alkyl lateral chains adsorb on the nanotube surface; (ii) the binding energy is stronger when the polymer backbone is more flexible; (iii) the purity of the dispersions seems to depend on a strong polymer–nanotube interaction.

Two anthracene-based copolymers, the thiophene-bridged carbazole-anthracene copolymer (abbreviated as PCBZANT) and the thiophene-bridged triphenylamine-anthracene copolymer (abbreviated as PTPAANT), have been developed as the hole-transporting materials (HTMs) for the inverted perovskite solar cells. They were thermally stable with decomposition temperatures of 435 and 420 °C. The High Occupied Molecular Orbitals (HOMO) of −5.15 and −5.24 eV of two copolymers facilitated the hole carriers transfer from the perovskite layer (CH 3 NH 3 PbI 3 , HOMO: −5.4 eV) in contrast to poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS, HOMO: −4.9 eV). The solar cell with PCBZANT (abbreviated as the PCBZANT device) showed the highest power conversion efficiency (PCE) of 15.50%, while the cell with PTPAANT (abbreviated as the PTPAANT device) showed the highest PCE of 14.52%, with increases of 36.2% and 27.6%, respectively, relative to the PEDOT:PSS device. The thorough analysis disclosed that the high performance was mainly ascribed to the enhanced open-circuit voltage (V OC ) and short-circuit current density (J SC ), being contributed from the efficient hole-carrier extraction, the high hole mobility of two copolymers, and the high-quality perovskite film with large crystal size and less defect. With strong absorption in the range of 350−500 nm, the polymers decreased the destruction of UV-radiation on the perovskite layer as UV-filters and improved the stability of the inverted cells.

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Poly[(2,1,3‐benzothiadiazole‐4,7‐diyl)‐alt‐4′,3′′‐difluoro‐3,3′′′‐di(2‐octyldodecyl)‐2,2′;5′,2′′;5′′,2′′′‐quaterthiophene‐5,5′′′‐diyl)] (PBTff4T‐2OD) and poly[(5,6‐difluoro‐2,1,3‐benzothiadiazol‐4,7‐diyl)‐alt‐3,3′′′‐di(2‐octyldodecyl)‐2,2′;5′,2′′;5′′,2′′′‐quaterthiophene‐5,5′′′‐diyl)] (PffBT4T‐2OD) for use as the p‐donor component of high‐efficiency fullerene‐based organic solar cells are usually synthesized in established C−C cross‐coupling reactions, preferably using the Stille procedure. This report describes how PBTff4T‐2OD and PffBT4T‐2OD are generated in a direct arylation polycondensation (DAP) approach with molecular weights up to Mn=19.4 kDa and 21.1 kDa, respectively, and how structural defects in the copolymers (e. g., homocoupling defects) show a strong impact on the pre‐aggregation behavior. The optimized reaction conditions allow for a distinct reduction of the amount of such defects in the resulting copolymers. When the Stille‐type products are used in the active layer of organic solar cells (OCSs) together with fullerene acceptors, high power‐conversion efficiencies (PCEs) in the range of 8.6–10.8 % have been reported. The high PCEs are particularly related to the pre‐aggregation of the conjugated copolymers prior to film formation. Despite quite similar characterization data, non‐optimized OCSs with the DAP polymers as replacement for the Stille products afforded a relatively low power‐conversion efficiency of up to 2.4 %.