Organic molecules, tools for the intelligent design of new photovoltaics.

The presence of spin ordering in a non-magnetic metallic host due to molecular charge transfer has dramatic effects on the magnetic and transport properties of the system. The control of the spin ordering at well-defined hybrid interfaces is a crucial component to engineer the performance of future organic spintronic devices. Through this proposal we aim to investigate the possibility of using organic molecule (C60) with various metals to create new materials. Various magnetic, electrical and optical measurements will be performed with a focus to investigate the charge transfer process between organic molecule and metallic materials in the hybrid. Our primary work focuses on photovoltaic devices but our advances in understanding and creating new materials and processes will take important part of this project.

The presence of spin ordering in a non-magnetic metallic host due to molecular charge transfer has dramatic effects on the magnetic and transport properties of the system. The control of the spin ordering at well-defined hybrid interfaces is a crucial component to engineer the performance of future organic spintronic devices. Through this proposal we aim to investigate the possibility of using organic molecule (C60) with various metals to create new materials. Various magnetic, electrical and optical measurements will be performed with a focus to investigate the charge transfer process between organic molecule and metallic materials in the hybrid. Our primary work focuses on photovoltaic devices but our advances in understanding and creating new materials and processes will take important part of this project.

Tailoring the magnetic properties at hybrid interfaces is a crucial requirement in engineering the performance of future molecular spintronic devices. Hybrid metallo-carbon states are formed due to charge transfer and hybridization between the d-orbitals of transition metals and the ? carbon electrons. These states strongly affect the electronic and magnetic properties of both materials due to a spin polarized charge transfer [6]. This interfacial effect may lead to the transformation of a non magnetic element, such as copper or manganese, into a magnetic material when it is in contact with carbon-based organic molecules [7,8,9]. When an organic molecule is brought into contact with a metal surface, it experiences two main bonding mechanisms: physisorption and chemisorption. These interactions influence the orbitals of the molecule and the surface of the metal and hence lead to a change in the electronic and magnetic properties of the molecule and the metal surface at the interface. The physisorption interaction is characterised by weak van der Waals interactions [10] that cause a broadening of the molecular electronic levels due to their proximity to the metallic states. Also, the surface-molecule interaction leads to rearrangement of the electron density and modifies the alignment of the molecular orbitals close to Fermi level [11]. In contrast to physisorption, the chemisorption interaction between the molecule and the metal leads to the formation of a new quantum mechanical system. This is due to strong charge transfer and hybridisation between the molecular orbitals (?-orbitals) and the metallic states (d-states), namely ?-d hybrid interfacial states. The hybrid states have mixed molecule-metal characteristics that may turn out to be very different from the isolated molecule or metal (i.e. chemical, electronic and magnetic) [13]. When the molecular film is sandwiched between two metallic electrodes, the current flows through molecular film is preserved. If the current is polarized, when the ferromagnetic electrodes are used, then the electrical current flow will change and that depends on the relative orientation of the magnetization of the electrodes (20?26). The change in electric current under the application of a magnetic field can be used into different spintronics applications that involve electrical switching. Also, irradiate such molecular devices to light has shown photovoltaic effect (Sun et al., Science 357, 677?680 (2017)). Several photoactive materials can be sandwiched between two electrodes and used as photovoltaic devices that convert solar energy to electrical energy.