Current Research Interest. Members of the Emory Renewable Energy Research and Education Consortium are engaging in a wide range of highly collaborative multidisciplinary renewable research topics, including catalyst development, novel materials synthesis, fundamental exciton and carrier dynamics in nanomaterials, bio-inspired hybrid photocatalysts, new solar energy conversion concepts (triplet upconversion and plasmon-induced hot electron transfer).
Novel low-dimensional nanomaterials. The Emory team targets fundamental understanding of exciton dynamics in two sets of two-dimensional (2D) quantum well (QW) materials and heterostructures. The Lian group studies colloidal 0D quantum dots, 1D nanorods and 2D nanoplatelets (NPLs) of cadmium and Lead chalcogenide and perovskite. The Srivastava group investigates exciton dynamics in 2D transition metal (W, Mo) dichalcogenide (TMD) nanosheets and heterostructures. For both sets of materials, their performance in solar energy conversion and optoelectronics depends critically on the exciton and charge carrier dynamics within the materials, across the heterojunctions and at their interface with electron and hole acceptors. These dynamics will be probed with ultrafast transient absorption (TA), transient reflection (TR) and time-resolved photoluminescence (PL) spectroscopic methods.
Bio-nanomaterials (Conticello, Lynn, Warncke)
Catalyst development (Hill and Musaev)
Hybrid nanostructure/enzyme for solar driven H2 generation (Dyer). The Dyer group is integrating inorganic nanomaterials with enzymes (such as hydrogenases) to form efficient artificial photosynthetic systems for solar fuel generation. The function of such hybrid materials and devices depends critically on how the catalysts are attached to the inorganic materials and how the charges can be transferred across their interface. Structural and dynamics information will be gained through detailed nonlinear and time-resolved spectroscopic studies.
Hybrid inorganic/organic materials for upconversion of low energy photons (Lian, Evangelista). The efficiency of current semiconductor-based solar energy conversion devices is limited by the inefficient use of high energy photons (thermalization of high energy carriers to the conduction band edge) and the lack of absorption of low energy photons below the band gap, which gives rise to the Shockley-Queisser limit. Further improvement of efficiency beyond this limit requires new concepts of utilizing hot electrons and upconversion low energy photons. To address the latter challenge, Co-PI Egap will lead this collaborative team to develop hybrid quantum dot/organic polymer materials that are capable of converting two low energy photons into one high energy photon/excitation. The upconversion process depends on the efficient generation of two long-lived triplet states and their efficient annihilation to form a higher energy singlet state. The design and development of these materials requires intimate knowledge of dynamics of both triplet and singlet states in these materials, which can be gained through the use of the advanced spectroscopic tools (both transient absorption and time-resolved photoluminescence). The success of such project depends critically on the ability of the collaborative team to design novel polymer and inorganic materials (Lian), to model their electronic structure (Evangelista), and to probe their ultrafast energy transfer dynamics (Lian).
Plasmon-induced hot electron transfer at semiconductor/metal interface (Harutyunyan and Lian). Recent advances in plasmonic materials have led to interesting new approaches for solar energy conversion. Among them, plasmon induced hot electron transfer at the semiconductor/metal interface leads to unexpected use of metal as light harvesting materials, which greatly expands the material choices for solar energy harvesting. Combined with catalytic properties of metals, this phenomenon offers exciting new directions for solar energy research. Co-PI Harutyunyan will lead this effort in fabricating new plasmonic metal/2D semiconductor materials and characterize the hot electron transfer efficiency in these materials.