To co-assemble organic and inorganic precursors into opto-electronically functional hybrid materials and interfaces for high performance devices.
Research-Past and current projects:
Intercalation of conjugated polymers/molecules into the galleries of 2D-layered compounds
2D host layered structures, such as clays, layered metal oxides and layered metal chalcogenides, have sheet-like structures that are characterized by strong covalent bonds within the layers and weak van der Waals forces between the layers. Consequently, the interlayer space can be separated considerably to incorporate guest polymer species while preserving the integrity of the layer structure. We developed a general synthetic methodology to incorporate conjugate polymers into MX2-hosts towards specific applications and synergism.
Self-assembly into Mesostructured Metal Oxide Films Containing Conjugated Polymers:
One promising class of nanocomposites is based on the incorporation of organic functional molecules into a mesoscopically ordered inorganic matrices. This offers prospects for property-adjustments according to interactions of the functional organic species with each other, with the organic structure-directing agents, and/or with the inorganic host. Several synthetic approaches have been developed and explored in our group for the deposition of highly ordered metal oxides mesostructures, such as titania and silica matrices, with incorporated conjugated polymers and/or organic dyes. Variation of the synthetic parameters allowed us to tailor the interface between the organic and inorganic phases and control their distance at the nanometer scale.
We developed a new and improved protocol for processing hybrid photovoltaic films using ALD, atomic layer deposition. We demonstrated, for the first time, that ALD can be used to deposit hybrid photovoltaic films with exceptional control over film composition and morphology. The hybrid system is prepared by exposing a pre-formed conjugated polymer film to an ALD alternating sequence of a metal oxide precursor and water.
We reported a general strategy for generating white photoluminescence (PL) and electroluminescence (EL) from a single hybrid material. The white-emitting hybrid material is composed of red, green, and blue (RGB) emissive conjugated polymers confined into the galleries of an inorganic layered host material. The semiconducting inorganic host not only supports the transport of charge carriers, but also serves as a barrier to energy transfer between the intercalated polymer chains. By significantly reducing this energy transfer, emission from the three RGB chromophores is observed simultaneously.
We undertook one of the greater challenges in the field of hybrid organic/inorganic photovoltaics: generating a donor-acceptor interpenetrating network structure with, one the one hand, phase separation on a sub 20 nm length scale, yet continuous and oriented over the much longer length scale of an operating device. To achieve this goal we developed few synthetic approaches including self-organization and ALD. The interpenetrating conjugated polymer and metal oxide networks with ~15 nm organic-inorganic phase separation were integrated into photovoltaic devices and resulted in high open circuit voltages, reasonable photocurrent, and good photovoltaic efficiency.
Another hybrid system we study is the organic/metal interface i.e. the active layer/electrode interface. Organic/metal interactions are studied to enhance charge collection/injection from the organic active layer to the metal electrode. We developed the spontaneous formation of interlayers at buried organic/metal interfaces through small molecule migration. Using this approach we were able to double the efficiency of the P3HT:PCBM devices prepared to over 4%.
We designed, synthesised and integrated hybrid mesostructured electrode for fast-switching all-solid-state EC devices. The electrode was composed of a porous WO3 film infiltrated with Nafion and topped with a thick Nafion layer acting as proton reservoir for the device. The high WO3/Nafion interfacial area and improved contact in the mesostructured hybrid electrode facilitates proton intercalation and de-intercalation. The mesostructured hybrid electrode exhibited a dramatic reduction of the EC response-time and sustained over 100 coloration-bleaching cycles with minor loss in optical contrast during cycling even without sealing of the device.