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Local thermal management has important implications regarding comfort, energy consumption, and electronic device performance/lifetime. While organic thermoelectrics have emerged as promising materials for flexible thermoelectric energy harvesting devices, their potential as Peltier cooling element has been largely overlooked. Here, micro-thermoelectric coolers based on doped small molecule thin-films with a fast response time (around 25 µs) which is among the fastest micro-thermoelectric coolers reported are presented. This experimental cooling performance is supported by simulation using the finite-element method for thermal transport. The results show that organic thermoelectrics offer great potential for flexible and wearable micro-thermoelectric cooling applications.

Carbon-based semiconductors such as conjugated organic polymers are of potential use in the development of spintronic devices and spin-based information processing. In particular, these materials offer a low spin–orbit coupling strength due to their relatively light constituent chemical elements, which should, in principle, favour long spin diffusion lengths. However, organic polymers are relatively disordered materials and typically have a carrier mobility that is orders of magnitude lower than crystalline inorganic materials. As a result, small spin diffusion lengths of around 50 nm have typically been measured using vertical organic spin valves. Here, we report measuring spin diffusion lengths in doped conjugated polymers using a lateral spin transport device architecture, which is based on spin pumping injection and inverse spin Hall detection. The approach suggests that long spin diffusion lengths of more than 1 μm and fast spin transit times of around 10 ns are possible in conjugated polymer systems when they have a sufficiently high spin density (around 1020 cm−3). We explain these results in terms of an exchange-based spin diffusion regime in which the exchange interactions decouple spin and charge transport., info:eu-repo/semantics/published

Summary form only given. Organic semiconductors (OSC) such as conjugated polymers/molecules are enabling flexible, large area optoelectronic devices, such as organic light-emitting diodes, transistors, and solar cells. Due to their exceptionally long spin lifetimes, these carbon-based materials could also have an important impact on spintronics, where carrier spins play a key role in transmitting, processing and storing information. Here, we combine three different approaches to study spin transport in OSC: spin pumping induced by ferromagnetic resonance (FMR), vertical and lateral spin-valves. i) We have recently demonstrated spin pumping by FMR in a ferromagnet (FM)/ conjugated polymer/nonmagnetic (NM) spin-sink trilayer to demonstrate the ability of polarons to carry pure spin currents over hundreds of nanometers with long spin relaxation times of up to a millisecond and to exhibit Hanle precession. Our trilayer architecture relies on spin pumping from a FM material for spin injection into the organic and on the inverse spin-Hall effect (ISHE) in a NM metal with strong spin-orbit coupling for detection of spins transmitted through the organic layer. This technique allows us to measure both spin and charge carrier transport through the organic in the same device. We have also studied spin pumping on different organic materials such as PBTTT, F4TCNQ doped PBTTT as well as P3HT with a thickness dependence in order to characterize the spin diffusion length of the organic layer. ii) We report the results of magnetoresistance (MR) measurements in vertical organic spin-valves where an organic material is contacted by two FM electrodes (Py) with the magnetic field oriented parallel to the layer stack. The organic layer is generally thick enough to avoid any coupling between the two FM electrodes. The MR is measured as a function of temperature, bias and orientation. iii) Finally, we report our attempts at spin injection into OSC using lateral organic spin-valves (LSV). W, info:eu-repo/semantics/published