Doping is one of the most important methods to control charge carrier concentration in semiconductors. Ideally, the introduction of dopants should not perturb the ordered microstructure of the semiconducting host. In some systems, such as modulation-doped inorganic semiconductors or molecular charge transfer crystals, this can be achieved by spatially separating the dopants from the charge transport pathways. However, in conducting polymers, dopants tend to be randomly distributed within the conjugated polymer, and as a result the transport properties are strongly affected by the resulting structural and electronic disorder. Here, we show that in the highly ordered lamellar microstructure of a regioregular thiophene-based conjugated polymer, a small-molecule p-type dopant can be incorporated by solid state diffusion into the layers of solubilizing side chains without disrupting the conjugated layers. In contrast to more disordered systems, this allows us to observe coherent, free-electron-like charge transport properties, including a nearly ideal Hall effect in a wide temperature range, a positive magnetoconductance due to weak localization and the Pauli paramagnetic spin susceptibility.

This work provides an efficient way to facilitate both electron and hole extraction in the designated interfaces of perovskite solar cells. A record power conversion efficiency of 23.6% for mixed Sn–Pb perovskite solar cell devices is realized.

A clear correlation between the number of accumulated holes (Nspin) in poly(3‐hexylthiophene) (P3HT) and the deterioration of the performance is observed in polymer solar cells under simulated solar irradiation. The sites of hole accumulation with deep trapping levels are formed at the interfaces between P3HT:[6,6]‐phenyl C61‐butyric acid methyl ester (PCBM) and poly(3,4‐ethylenedioxythiophene):poly(4‐styrenesulfonate) (PEDOT:PSS) layers.

An electron spin resonance (ESR) method is applied to a pentacene field-effect device to investigate gate-induced hole carriers in such devices. Clear field-induced ESR signals are observed, demonstrating that all of the field-injected carriers have S = 1/2 spins. Anisotropic ESR signals due to unpaired pi electrons show the molecular orientation at the interface in the devices. The spatial extent of the spin density distribution (wave function) of the carriers is evaluated from the ESR linewidth, accounting for the hyperfine structure, to be of the order of 10 molecules.