Research Projects

In recent years, metal halide perovskites have drawn considerable interest in optoelectronic applications, due to their fascinating properties, such as high absorption coefficients, long charge carrier diffusion lengths, low trap densities, tunable band gaps, and excellent defect tolerance. Yet, the ongoing research is limited to single-phase perovskite materials. To compensate the growing materialistic needs, fabricating heterostructures of perovskites with potential materials has stemmed diversely. The unique properties of heterostructures can be harnessed to exploit extended charge separation, reduce recombination losses, and deliver innovative features through tailored band alignment. However, despite their promise, the underlying ultrafast charge carrier dynamics, separation, trapping, transfer, and recombination, are rarely investigated. This research gap impedes the logical development of state-of-the-art perovskite-based devices. To date, most of the research is focused on CsPbBr3-based heterostructures due to their high phase stability and proficient emission properties. Conversely, there are very few reports on CsPbCl3 and CsPbI3-based heterostructures. CsPbCl3, a wide-bandgap perovskite predominantly emitting in the ultraviolet region, is relevant to high-energy photonics. CsPbI3, having a suitable photovoltaic bandgap (~1.7 eV), still suffers from low PLQY and phase instability, respectively. These limitations have obstructed the efficient design of heterostructures for any real-time application. Apart from these lead halide perovskites, lead-free perovskite based heterostructures are an alternative solar harvesting material due to their environmental friendliness. But these materials face challenges such as weak photoluminescence, low carrier mobility, and intrinsic defects. Despite recent progress in demonstrating lead-free perovskites at the device level, their application within heterostructures remains unexplored. To overcome their poor optoelectronic performance, interface engineering plays a vital role by promoting effective carrier extraction, mitigating defect states, and enabling spatial separation of charge carriers. The lack of a comprehensive understanding of carrier dynamics underscores the pressing need to investigate lead-free perovskite heterojunctions. Another paradigm that has been in focus recently but not much explored is the integration of perovskites with plasmonic semiconductors. They exhibit strong localized surface plasmon resonances ranging from UV-Vis to NIR region and can inject hot carriers or enhance optical fields at the perovskite interface. They can be attributed to tunable Fermi levels, cost-effectiveness, and facile synthetic methods. Nonetheless, perovskite–plasmonic semiconductor heterostructures remain unexplored, particularly the femtosecond charge transfer rates, which are crucial for optoelectronic applications. A fundamental shortcoming common to all of these heterostructures is the absence of an in-depth investigation of ultrafast interfacial processes. Key concerns on the carrier migration pathway, transfer rate, role of trap states, hot carrier lifetimes, and correlating these findings into material performance remain unresolved. Ultrafast time-resolved techniques offer the tools to probe these dynamics on timescales ranging from femtoseconds to microseconds. However, few studies have employed these methods systematically across numerous heterostructures to gain profound insights into quasi-particle generation and their interaction. Our proposal aims to solve a significant barrier in perovskite heterostructure research like a lack of knowledge of interfacial ultrafast dynamics, particularly in perovskite compositions, lead-free systems, plasmonic hybrids and most importantly, epitaxial heterostructure formation. This effort will pave the road for novel device designs and environmentally sustainable technologies by expanding fundamental understanding.