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Abstract The design of polymeric semiconductors exhibiting high electrical conductivity (σ) and thermoelectric power factor (PF) will be vital for flexible large‐area electronics. In this work, four polymers based on diketopyrrolopyrrole (DPP), 2,3‐dihydrothieno[3,4‐b][1,4]dioxine (EDOT), thieno[3,2‐b]thiophene (TT), and 3, 3′‐bis (2‐(2‐(2‐methoxyethoxy) ethoxy) ethoxy)‐2, 2′‐bithiophene (MEET) are investigated as side‐chains, with the MEET polymers newly synthesized for this study. These polymers are systematically doped with tetrafluorotetracyanoquinodimethane ( F₄TCNQ), CF3SO3H, and the synthesized dopant Cp(CN)₃‐(COOMe)₃, differing in geometry and electron affinity. The DPP‐EDOT‐based polymer containing MEET as side‐chains exhibits the highest conductivity (σ) ≈700 S cm−1 in this series with the acidic dopant (CF₃SO₃H). This polymer also shows the lowest oxidation potential by cyclic voltammetry (CV), the strongest intermolecular interactions evidenced by differential scanning calorimetry (DSC), and has the most oxygen‐based functionality for possible hydrogen bonding and ionic screening. Other polymers exhibit high σ ≈300–500 S cm−1 and power factor up to 300 µW m⁻¹K⁻². The mechanism of conductivity is predominantly electronic, as validated by time‐dependent conductance studies and transient thermo voltage monitoring over time, including for those doped with the acid. These materials maintain significant thermal stability and air stability over ≈6 weeks. Density functional theory calculations reveal molecular geometries and inform about frontier energy levels. Raman spectroscopy, in conjunction with scanning electron microscopy (SEM‐EDS) and x‐ray diffraction, provides insight into the solid‐state microstructure and degree of phase separation of the doped polymer films. Infrared spectroscopy enables this study to further quantify the degree of charge transfer from polymer to dopant. 

Widespread testing and isolation of infected patients is a cornerstone of viral outbreak management, as underscored during the ongoing COVID-19 pandemic. Here, we report a large-area and label-free testing platform that combines surface-enhanced Raman spectroscopy and machine learning for the rapid and accurate detection of SARS-CoV-2. Spectroscopic signatures acquired from virus samples on metal–insulator–metal nanostructures, fabricated using nanoimprint lithography and transfer printing, can provide test results within 25 min. Not only can our technique accurately distinguish between different respiratory and nonrespiratory viruses, but it can also detect virus signatures in physiologically relevant matrices such as human saliva without any additional sample preparation. Furthermore, our large area nanopatterning approach allows sensors to be fabricated on flexible surfaces allowing them to be mounted on any surface or used as wearables. We envision that our versatile and portable label-free spectroscopic platform will offer an important tool for virus detection and future outbreak preparedness. 

Abstract Efficient doping of polymer semiconductors is required for high conductivity and efficient thermoelectric performance. Lewis acids, e.g., B(C₆F₅)₃, have been widely employed as dopants, but the mechanism is not fully understood. 1:1 “Wheland type” or zwitterionic complexes of B(C₆F₅)₃are created with small conjugated molecules 3,6‐bis(5‐(7‐(5‐methylthiophen‐2‐yl)‐2,3‐dihydrothieno[3,4‐b][1,4]dioxin‐5‐yl)thiophen‐2‐yl)‐2,5‐dioctyl‐2,5‐dihydropyrrolo[3,4‐c]pyrrole‐1,4‐dione [oligo_DPP(EDOT)₂] and 3,6‐bis(5''‐methyl‐[2,2':5',2''‐terthiophen]‐5‐yl)‐2,5‐dioctyl‐2,5‐dihydropyrrolo[3,4‐c]pyrrole‐1,4‐dione [oligo_DPP(Th)₂]. Using a wide variety of experimental and computational approaches, the doping ability of these Wheland Complexes with B(C₆F₅)₃are characterized for five novel diketopyrrolopyrrole‐ethylenedioxythiophene (DPP‐EDOT)‐based conjugated polymers. The electrical properties are a strong function of the specific conjugated molecule constituting the adduct, rather than acidic protons generated via hydrolysis of B(C₆F₅)₃, serving as the oxidant. It is highly probable that certain repeat units/segments form adduct structures inp‐type conjugated polymers which act as intermediates for conjugated polymer doping. Electronic and optical properties are consistent with the increase in hole‐donating ability of polymers with their cumulative donor strengths. The doped film of polymer (DPP(EDOT)₂‐(EDOT)₂) exhibits exceptionally good thermal and air‐storage stability. The highest conductivities, ≈300 and ≈200 S cm⁻¹, are achieved for DPP(EDOT)₂‐(EDOT)₂doped with B(C₆F₅)₃and its Wheland complexes.