# The Effect of Local Doping of the Polymer-Polymer Interface Using Cu\({}_{2}\)O Particles
## 1 Introduction  
Conjugated polymer materials are an important object for the development of electronics and, in particular, organic electronics. They are of scientific interest from the point of view of the synthesis of new compounds with unique properties and the development of new unique applications, including spintronics, optoelectronics, light-emitting diodes and many more [1, 2]. It was established that a two-dimensional region with electronic properties different from the volume can occur (or form) along the interface of two organic dielectrics [3, 4]. Explanations of anomalous electronic properties (high conductivity and high mobility of charge carriers) were given on the basis of the quasi-two-dimensional (q2 DEG) electron gas model. However, the reasons for the appearance of new electronic properties along the interface of two organic dielectrics, [3] and [4], are still debatable. In particular, in [3] it is assumed that a two-dimensional region is formed because of its analogy to semiconductor heterostructures and due to the contact phenomena resulting from the difference in the spectrum of the electronic states, tetrathiofulvalene (TTF) and 7,7,8,8-tetracyanoquinodimethane (TCNQ). In [4], such an explanation was impossible, since the contact of two dielectric polymer films with the same electron spectrum from the class of polyarylene phthalides-polydiphenylene phthalide (PDPh) was used. PDPh is not a conjugated polymer, unlike most electrically conductive polymers. The monomeric link of its structure contains a skeletal part consisting of alternating biphenyl fragments (Figure 1a). The biphenyl fragments are separated by phthalide groups (PGs). PGs are parts of a polymer monomer due to the lack of bonding of valence \(\pi\) electrons along the polymer chain. PGs are large molecular groups with a relatively large dipole moiety. In this regard, phthalide groups on the surface of the films form brushes when forming films from PDPh [5]. This is a well-known thermodynamic effect, which is often used to impart the desired properties to a poly-dimensional surface [6]. In this regard, the authors proposed an interpretation of the results of the study of electronic properties along the polymer-polymer boundary based on the \"polar catastrophe\" model previously proposed for the contacts of two inorganic dielectrics from the class of LaAlO3/SrTiO3 perovskites [7]. This choice was due to the fact that these compounds included side phthalide groups of atoms with a large dipole moment, which is a necessary condition for the applicability of this model. Subsequently, in [8; 9; 10], the \"polar catastrophe\" model proved itself in explaining electrophysical phenomena occurring at the interface of two organic films with a wide band gap. Previous studies [4; 9; 10] have shown that if the technology of manufacturing multilayer polymer structures is followed, a transition layer localized within several monomolecular layers can be formed between two films of organic dielectrics. Unlike perovskite films, polymer films were made via centrifugation from a polymer solution. It is obvious that the electrophysical parameters of this region should strongly depend on the conditions of preparation of a two-layer film (solvent, concentration of solutions, rotation speed of the centrifuge, annealing temperature, ambient atmosphere, humidity, etc.). In addition, it is always necessary to take into account the possibility of current leakage through the surface of the upper film, along the interface of the polymer film/substrate and directly through the polymer. All these current flow paths are difficult to control experimentally. Thus, it requires a large number of additional experiments with various sample configurations [8]. In this regard, it seems important to be able to indicate the paths of current flow between two electrodes in contact with the polymer-polymer interface. The idea of the ex  
Figure 1: (**a**) Structural formula of PDPh.