As conducting polymers become increasingly important in electronic devices, understanding their charge transport is essential for material and device development. Various semi-empirical approaches have been used to describe temporal charge carrier dynamics in these materials, but there have yet to be any theoretical approaches utilizing ab initio molecular dynamics. In this work, we develop a computational technique based on ab initio Car-Parrinello molecular dynamics to trace charge carrier temporal motion in archetypical conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT). Particularly, we analyze charge dynamics in a single PEDOT chain and in two coupled chains with different degrees of coupling and study the effect of temperature. In our model we first initiate a positively charged polaron (compensated by a negative counterion) at one end of the chain, and subsequently displace the counterion to the other end of the chain and trace polaron dynamics in the system by monitoring bond length alternation in the PEDOT backbone and charge density distribution. We find that at low temperature (T = 1 K) the polaron distortion gradually disappears from its initial location and reappears near the new position of the counterion. At the room temperature (T = 300 K), we find that the distortions induced by polaron, and atomic vibrations are of the same magnitude, which makes tracking the polaron distortion challenging because it is hidden behind the temperature-induced vibrations. The novel approach developed in this work can be used to study polaron mobility along and between the chains, investigate charge transport in highly doped polymers, and explore other flexible polymers, including n-doped ones.

Understanding charge carrier transport in conductive polymers is imperative for the materials' synthesis and optimizing devices. While most theoretical studies utilize time-independent approaches for describing charge transport, there is an interest in addressing temporal charge carrier dynamics, which provides more information than time-independent methods. In this study, ab initio molecular dynamics is utilized to gain microscopic insights into charge carrier temporal dynamics in PEDOT. It is demonstrated that transport along the chains is band-like and across the chains is hopping-like. Polaron mobility is calculated along the chains to be 4 cm2 V-1 s-1, providing a theoretical upper limit in thiophene-based conducting polymers. Also, by tracing polaron jumps between chains, the hopping rate, aligning with Marcus' theory is extracted. If an electric field can release polarons from Coulomb traps is investigated, finding that the necessary field strength surpasses typical experimental values. Two regimes of intrachain polaron movement are found: under low/intermediate electric fields, polaron moves velocity-constantly with coupled charge and lattice distortion, while under high electric fields, charge and lattice distortion decouple. The methodology applies to studying mobilities in p- and n-doped conjugated polymers, including highly doped systems with more polymer chains, and incorporates dielectric screening to address the impact of shallow and deep traps. In this study, the researchers employ the ab initio molecular dynamics technique to acquire microscopic insights into charge carrier temporal dynamics in PEDOT. It is demonstrated that transport along the chains is band-like (temperature-independent), and across the chains is hopping-like (temperature-induced). The calculated polaron mobility along the chains establishes a theoretical upper limit for charge carrier mobility in thiophene-based conducting polymers. image

The surge in the number of distributed microelectronics and sensors requires versatile, scalable, and affordable power sources. Heat-harvesting organic thermoelectric generators (TEGs) are regarded as potential key components of the future energy landscape. Recent advances in the performance of organic thermoelectric materials have made practical applications of organic TEGs more feasible than ever before, yet the challenges of designing and fabricating organic TEGs suitable for real scenarios are scarcely addressed. Specifically, small sensors and wearables demand for micro-thermoelectric generators (mu TEGs) with high power density architectures and small form factors, while typical demonstrations of organic TEGs are characterized by < 10 thermocouples (TCs) per cm(2). This work presents a rolled, organic mu TEG architecture combining large-area, solution-based deposition techniques, such as inkjet and spray-coating, and an ultrathin parylene substrate to achieve a thermocouple density of 1842 TCs cm(-2). Such demonstrative mu TEG reaches a thermoelectric conversion performance of 0.15 mu W cm(-2) at Delta T = 50 K. Such power output is well in line with finite element method simulations, which highlight the benefit of the architecture and show that remarkable power densities, in the mW cm(-2) range at Delta T = 10 K, are realistically achievable with geometrical improvements and already ongoing advancements in organic thermoelectric inks.