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Abstract The sensing properties of poly 3‐(3‐carboxypropyl) thiophene‐2,5‐diyl (PT‐COOH) and hydroxylated polythiophene (PT‐OH) as bioreceptor layers were studied and are discussed in this paper. The polymer films cover the channel region of the OECT devices and anti‐human IgG was immobilized on the polymer films. We use threshold voltage (Vth) change as a sensing signal to detect the interaction between anti‐human IgG and human IgG. By adding different concentrations of human IgG, Vth difference can be observed on anti‐human IgG immobilized polymer films, with optimized detection from a blend of the two polymers. Open circuit potential (OCP) measurement was also done on the OECT devices based on the same anti‐human IgG and human IgG interaction pair to help us understand the mechanism behind the antibody functionalization and the interaction between antibody and antigen. Importantly, the observed positive OCP change for the PT‐OH system was self‐consistent with the negative OECT Vth change that was obtained, since the latter is applied to the gate while the former is measured at the channel. 

Abstract Operational stability and sensitivity are key issues for the practical application of organic field‐effect‐transistor (OFET)‐based sensors. Instability over time due to intrinsic device bias stress and conductance drift induced by the ambient environment can obscure responses to analytes of interest. These instabilities are well‐known hindrances to the practical application of OFET sensors. It is demonstrated for the first time that an innovative and simple two‐OFET circuit design can effectively compensate the drifts originating from bias stress and/or the environment while maintaining chemical sensitivity and increasing signal‐to‐noise ratio. This is enabled by illumination of one photosensitive OFET to compensate the drift of the other chemical‐sensing OFET, though in principle a pair of OFETs with opposing drifts generated by any mechanism could be used. The circuit, compared with individual OFET‐based sensors, achieves significantly increased environmental stability, and its enhanced response to chemical vapors is also demonstrated by detecting the representative pollutants nitrogen dioxide (NO₂) and ammonia (NH₃). This shows that OEFTs with drifts being compensated by any mechanism can lead to stabilized sensor circuits. 

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. 

Abstract A systematic analysis is used to understand electrical drift occurring in field‐effect transistor (FET) dissolved‐analyte sensors by investigating its dependence on electrode surface‐solution combinations in a remote‐gate (RG) FET configuration. Water at pH 7 and neat acetonitrile, having different dipoles and polarizabilities, are applied to the RG surface of indium tin oxide, SiO₂, hexamethyldisilazane‐modified SiO₂, polystyrene, poly(styrene‐co‐acrylic acid), poly(3‐hexylthiophene‐2,5‐diyl) (P3HT), and poly [3‐(3‐carboxypropyl)thiophene‐2,5‐diyl] (PT‐COOH). It is discovered that in some cases a slow reorientation of dipoles at the interface induced by gate electric fields causes severe drift and hysteresis because of induced interface potential changes. Conductive and charged P3HT and PT‐COOH increase electrochemical stability by promoting fast surface equilibrations. It is also demonstrated that pH sensitivity of P3HT (17 mV per pH) is an indication of proton doping. PT‐COOH shows further enhanced pH sensitivity (30 mV per pH). This combination of electrochemical stability and pH response in PT‐COOH are proposed as advantageous for polymer‐based biosensors. 

Abstract Two donor–acceptor (D–A) polymers are obtained by coupling difluoro‐ and dichloro‐substituted forms of the electron‐deficient unit BDOPV and the relatively weak donor moiety dichlorodithienylethene (ClTVT). The conductivity and power factors of doped devices are different for the chlorinated and fluorinated BDOPV polymers. A high electron conductivity of 38.3 and 16.1 S cm⁻¹are obtained from the chlorinated and fluorinated polymers with N‐DMBI, respectively, and 12.4 and 2.4 S cm⁻¹are obtained from the chlorinated and fluorinated polymers with CoCp₂, respectively, from drop‐cast devices. The corresponding power factors are 22.7, 7.6, 39.5, and 8.0 µW m⁻¹K⁻², respectively. Doping of PClClTVT with N‐DMBI results in excellent air stability; the electron conductivity of devices with 50 mol% N‐DMBI as dopant remained up to 4.9 S m⁻¹after 222 days in the air, the longest for an n‐doped polymer stored in air, with a thermoelectric power factor of 9.3 µW m⁻¹K⁻². However, the conductivity of PFClTVT‐based devices can hardly be measured after 103 days. These observations are consistent with morphologies determined by grazing incidence wide angle X‐ray scattering and atomic force microscopy. 

Abstract A pre‐formed Meisenheimer complex of a naphthalenediimide (NDI) with tetrabutylammonium fluoride (TBAF) is obtained in a simple way by mixing dibrominated 4,9‐dibromo‐2,7‐bis(2‐octyldodecyl)benzo[lmn][3,8]phenanthroline‐1,3,6,8(2H,7H)‐tetraone and TBAF in solution and used as a dopant for n‐type organic thermoelectrics. Two n‐type polymers PNDIClTVT and PBDOPVTT are synthesized, n‐doped, and characterized as conductive and thermoelectric materials. PNDIClTVT doped with NDI‐TBAF presents a high σ value of 0.20 S cm^–1, a Seebeck coefficient (S) of −1854 µV K^–1, and a power factor (PF) of 67 µW m^–1K^–2, among the highest reported PF in solution‐processed conjugated n‐type polymer thermoelectrics. Using 4‐(1,3‐dimethyl‐2,3‐dihydro‐1H‐benzoimidazol‐2‐yl)phenyl)dimethylamine and NDI‐TBAF as co‐dopants, PNDIClTVT has a PF > 35 µW m^–1K^–2; while for PBDOPVTT σ = 0.75 S cm^–1and PF = 58 µW m^–1K^–2. In this study it is found that an ionic adduct together with a neutral dopant improves the performance of n‐type organic thermoelectrics leading to an enhanced power factor, and more generally, the role of such an adduct in polymer doping is also elucidated. 

Abstract A novel n‐type copolymer dopant polystyrene–poly(4‐vinyl‐N‐hexylpyridinium fluoride) (PSpF) with fluoride anions is designed and synthesized by reversible addition–fragmentation chain transfer (RAFT) polymerization. This is thought to be the first polymeric fluoride dopant. Electrical conductivity of 4.2 S cm^–1and high power factor of 67 µW m^–1K^–2are achieved for PSpF‐doped polymer films, with a corresponding decrease in thermal conductivity as the PSpF concentration is increased, giving the highest ZT of 0.1. An especially high electrical conductivity of 58 S cm^–1at 88 °C and outstanding thermal stability are recorded. Further, organic transistors of PSpF‐doped thin films exhibit high electron mobility and Hall mobility of 0.86 and 1.70 cm²V^–1s^–1, respectively. The results suggest that polystyrene–poly(vinylpyridinium) salt copolymers with fluoride anions are promising for high‐performance n‐type all‐polymer thermoelectrics. This work provides a new way to realize organic thermoelectrics with high conductivity relative to the Seebeck coefficient, high power factor, thermal stability, and broad processing window.