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Doping dependent current-voltage (I-V) and capacitance-voltage (C-V) measurements were carried out on polypyrrole devices in metal-polymer-metal sandwich structure. Temperature dependent I-V measurements infer that space-charge limited conduction (SCLC) with exponential trap distribution is appropriate for the moderately doped samples, whereas trap-free SCLC is observed in lightly doped samples. Trap densities and energies are estimated, the effective mobility is calculated using the Poole–Frenkel model, and the mobility exhibits thermally activated behavior. Frequency dependent capacitance-voltage characteristics show a peak near zero bias voltage, which implies that these devices are symmetric with a negligible barrier height at the metal-polymer interface. Low frequency capacitance measurements have revealed a negative capacitance at higher voltages due to the processes associated with the injection and redistribution of space-charges.

Current–voltage (I–V) and impedance measurements were carried out in doped poly(3-methylthiophene) devices by varying the carrier density. As the carrier concentration reduces the I–V characteristics indicate that the conduction mechanism is limited by metal–polymer interface, as also observed in impedance data. The temperature dependence of I–V in moderately doped samples shows a trap-controlled space-charge-limited conduction (SCLC); whereas in lightly doped devices injection-limited conduction is observed at lower bias and SCLC at higher voltages. The carrier density-dependent quasi-Fermi level adjustment and trap-limited transport could explain this variation in conduction mechanism. Capacitance measurements at lower frequencies and higher bias voltages show a sign change in values due to the significant variations in the relaxation behaviour for lightly and moderately doped samples. The electrical hysteresis increases as carrier density is reduced due to the time scales involved in the de-trapping of carriers.

The current density–voltage (J–V) characteristics of poly(3-methylthiophene) devices show a negative differential resistance (NDR) at room temperature with a large peak to valley current ratio (∼507). This NDR can be tuned by two orders of magnitude by controlling the carrier density due to the variation of the space-charge region in the device. The temperature and scan rate dependent J–V measurements infer that the NDR is mainly driven by the trapping and de-trapping of carriers. The photo-generation of carriers is observed to reduce the NDR effect.

Polypyrrole (PPy) has been synthesized electrochemically on platinum substrate by varying synthesis temperature and dopant concentration. The charge transport in PPy has been investigated as a function of temperature for both in-plane and out-of-plane geometry in a wide temperature range of 5 K–300 K. The charge transport showed strong anisotropy and various mechanisms were used to explain the transport. The conductivity ratio, σr = σ(300 K)/σ(5 K) is calculated for each sample to quantify the relative disorder. At all the temperatures, the conductivity values for in-plane transport are found to be more for PPy synthesized at lower temperature, while the behavior is found to be different for out-of-plane transport. The carrier density is found to play a crucial role in case of in-plane transport. An effort has been made to correlate charge transport to morphology by analyzing temperature and frequency dependence of conductivity. Charge transport in lateral direction is found to be dominated by hopping whereas tunneling mechanisms are dominated in vertical direction. Parameters such as density of states at the Fermi level [N(EF)], average hopping distance (R), and average hopping energy (W) have been estimated for each samples in both geometry.

We report on the analysis of temperature-dependent current-voltage characteristics and impedance measurements of electrochemically doped poly(3-methylthiophene) devices at different doping levels. The extent of doping is carefully tailored such that only the bulk-limited transport mechanism prevails. A transition from exponentially distributed trap-limited transport to trap-free space-charge-limited current is observed in current-voltage conduction upon increasing the doping. The obtained trap densities (3.2 × 10 16 cm −3 and 8.6 × 10 15 cm −3 ) and trap energies (31.7 meV and 16.6 meV) for different devices signify the variation in disorder with doping, which is later supported by impedance measurements. Impedance-frequency data for various devices can not be explained using the parallel resistance-capacitance (RC) model in the equivalent circuit. However, this was established by incorporating a constant phase element Q (CPE) instead of the capacitance parameter. It should be emphasized that low doping devices in particular are best simulated with two CPE elements, while the data related to other devices are fitted well with a single CPE element. It is also observed from evaluated circuit parameters that the spatial inhomogeneity and disorder are the cause of variability in different samples, which has an excellent correlation with the temperature-dependent current-voltage characteristics.

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Interface-driven multifunctional facets are gearing up in the field of science and technology. Here, we present the interface-activated resistive switching (RS), negative differential resistance, diode behavior, and ultraviolet (UV) light sensing in nanosheet-based hybrid devices. A hybrid device i.e., titanium dioxide nanosheet (TiO 2 -NS)/poly(dimercaptothiadiazoletriazine)[Poly(DMcT-CC)] is fabricated by spin coating Poly-(DMcT-CC) polymer on hydrothermally as-grown TiO 2 -NS. The pristine devices of both materials show either small or no magnitude of RS, but the hybrid device shows highly enhanced RS of nearly four orders due to the formation of a p−n junction at the NS/polymer interface. The resistive random access memory feature appears to be more prominent in the hybrid device i.e., high and low current states are found to be stable in repetitive cycles since the interface acts as a trapping center for the carriers. The UV sensing ability of the hybrid device has been demonstrated by a threefold increment in a current at 60 mV. The impedance spectroscopy has been employed to show that the multifunctional features are directly associated to the NS/polymer interface, which deduce that the manipulation of such interfaces can pave the way for developing the hybrid structures.