Transport properties of doped conjugated polymers (CPs) have been widely analyzed with the Gaussian disorder model (GDM) in conjunction with hopping transport between localized states. These models reveal that even in highly doped CPs, a majority of carriers are still localized because dielectric permittivity of CPs is well below that of inorganic materials, making Coulomb interactions between carriers and dopant counterions much more pronounced. However, previous studies within the GDM did not consider the role of screening the dielectric interactions by carriers. Here we implement carrier screening in the Debye-Hückel formalism in our calculations of dopant-induced energetic disorder, which modifies the Gaussian density of states (DOS). Then we solve the Pauli master equation using Miller-Abrahams hopping rates with states from the resulting screened DOS to obtain conductivity and Seebeck coefficient across a broad range of carrier concentrations and compare them to measurements. Our results show that screening has significant impact on the shape of the DOS and consequently on carrier transport, particularly at high doping. We prove that the slope of Seebeck coefficient versus electric conductivity, which was previously thought to be universal, is impacted by screening and decreases for systems with small dopant-carrier separation, explaining our measurements. We also show that thermoelectric power factor is underestimated by a factor of ∼10 at higher doping concentrations if screening is neglected. We conclude that carrier screening plays a crucial role in curtailing dopant-induced energetic disorder, particularly at high carrier concentrations.

Abstract In this invited review article, we give a comprehensive account of the existing literature on the electronic properties of organic materials. The main focus of this article is the rich and extensive literature on the electronic transport in organic materials, particularly conjugated polymers, as they offer numerous advantages over inorganic materials. Consequently, they have found widespread application in photovoltaics, light-emitting displays, and even, more recently, in thermoelectric energy conversion. This literature review will be useful to researchers starting in the field of organic electronics as well as experts seeking to broaden their understanding of transport in polymers.

Fiber optics has revolutionized telecommunication with its superior bandwidth and distance it can span. For its use in IoT networks, some of the limiting factors are the high cost of new installations and the need to power the end device by electrical current. The installations are a part of long-term investments, and one can expect this to be an ever-smaller issue as more fibers are installed. Typically, the newly installed cables contain single-mode fibers. There are a lot of reports on transport of power over fiber, however, majority recommend using multi-mode fibers with a large core or double-clad fibers. In our approach, instead of increasing the core of the fiber, we focus on the possibility of shortening the working time of IoT devices, using the existing single-mode fiber for powering. Also, instead of an expensive PV (photo voltaic) cell with small dimensions and a high efficiency, we propose using the commercially available larger PV cells with an air gap between the end of the fiber and the cells. In accordance with our approach, we successfully conducted an experiment.