Conductivity of composite films based on conductive polymer PEDOT:PSS, graphene oxide and nanoparticles TiO$_{2}$ for contact layers of perovskite photovoltaic structures

The electrical properties of composite films based on conductive polymer PEDOT: PSS, graphene oxide (GO), and titanium dioxide nanoparticles (TiO$_2$) (PEDOT: PSS–TiO$_{2}$ and GO–TiO$_{2}$) used as contact layers of organic and perovskite photovoltaic structures have been studied. As a result of the study of morphology by atomic force microscopy, it was found that the PEDOT: PSS–TiO$_{2}$ and GO–TiO$_{2}$ films have a globular structure with a grain size of $\sim$200–300 nm. The current–voltage characteristics of the PEDOT: PSS–TiO$_{2}$ and GO–TiO$_{2}$ films are measured in the temperature range of 80–300 K, the dependences of the resistivity versus temperature, $\rho(T)$, which have an activation character, are obtained. It is established that as the temperature decreases, the $\rho(T)$ dependences show a transition from large values of the activation energy (570 meV and 329 meV) to lower values (25 meV and 2.2 meV) for the PEDOT: PSS–TiO$_{2}$ and GO–TiO$_{2}$ films, respectively. The mechanisms of transport of charge carriers in the materials studied are discussed.