Research Projects

Energy crisis is one of the pressing issues facing humanity today. In this scenario, solar energy has become the most promising renewable energy source around the globe and specifically in the countries like India which has huge solar power potential. Nevertheless, given the high cost, the light-harvesting efficiency of current commercial solar cells falls short to meet the projected global energy demands. Improving efficiency and search of low-cost materials requires in-depth investigation of their photophysical dynamics. In particular, energy and charge transfer processes that happens in ultrafast sub-picosecond, primarily governs the photon-conversion efficiency. Capturing these processes experiementally requires tools with femtosecond time resolution. The broad objective is to develop femtosecond time-resolved multidimensional spectroscopy tools to understand the underlying molecular mechanism of solar energy capture in light harvestings and optoelectronics. The outcome of light-matter interactions, such as quantum efficiency and reaction rate, depend upon energy dissipation pathways governed by intrinsic intra- and inter-molecular electronic interactions. The well-established concepts such as Förster energy transfer and Marcus electron transfer theory provide paramount guidance in understanding many photochemical processes. However, they are often inadequate in accurately predicting reaction outcomes due to the lack of precise structural dynamics information along excited state trajectories. This limitation is evident in many photochemical processes such as singlet fission, polaron formation, coherent energy transfer in antenna complexes etc. Some are reflected in our past research works. Thus, predicting the reaction dynamics becomes challenging, especially under conditions when the electronic and nuclear degrees are no longer independent as per the framework of Born-Oppenheimer approximation. This problem demands advanced sophisticated spectroscopic methods, which can capture correlated electronic-nuclear dynamics in real time and map out excited state trajectories on the potential energy landscape. We propose to develop the broadband femtosecond Transient Absorption (fsTA) as well as cutting-edge Time-resolved Coherent Raman Spectroscopy (TRCRS). The fsTA will examine energy dissipation pathways and exciton diffusion dynamics, while TRCRS will provide insights into coherent electron-nuclear interactions in ultrafast energy and electron transfer, potentially enabling control over these dynamics to achieve desirable outcomes. The proposed setup will be utilized to capture the primary ultrafast events of light harvesting from exciton transport to charge carrier diffusion with special emphasize on elucidating the role of electron-phonon coupling, which controls hot carrier cooling and polaron formation in organic photovoltaics. Overall, it will provide clear molecular level guidelines for improving new generation solar optoelectronic devices.