Charge carrier dynamics across the metal oxide/BaTiO3 interfaces toward photovoltaic applications from the theoretical perspective

Abstract

Transport layers in perovskite solar cells are the crucial parts in charge carrier extraction and transfer in the solar cell circuit. The physical and chemical properties of their interfaces with neighbouring layers, such as buffer layers, govern the dynamics of electrons across the interface boundaries. Using ab initio calculations, we study in detail the interface properties of metal oxide/BaTiO3 heterostructures. The structural changes near the metal oxide/BaTiO3 interfaces are detailed for the first time. The electronic properties are used to assess the quantities of interest for use in perovskite solar cells (band gap, effective mass, carrier mobility, plane averaged electrostatic potential, band offsets). The analysed results introduce several competing quantities which influence the charge dynamics: the band gap character versus the charge carrier effective mass and the averaged electrostatic potential difference versus the unfavourable conduction band offset. While experimental studies are unable to distinguish the relevance of the competing factors, our results point to the fact that BaTiO3 interlayer morphology plays a more important factor in the cell's performance than its intrinsic properties. Based on the results, general insights are given on the structural requirements for improved buffer layer materials in combinations with metal oxide transport layer used as substrates in the solar cell architecture.