Organic semiconductors

Within the context of organic electronics, our research is focused on understanding structure-property relationships in these technology relevant materials such as photovoltaic cells, field effect transistors and light-emitting diodes. Our goals and objectives are (i) identifying key structure-directing interactions that drive self-assembly of conjugated polymers, (iii) gaining insight into the interfacial structures and dynamics in bulk heterojunction morphologies, and (iii) understanding and addressing the fundamental questions related to the role of bulk and interfacial morphology on key processes such as charge generation, recombination, and extraction that dictate power conversion efficiencies (PCEs). In particular, we apply state-of-the-art solid-state NMR spectroscopy in conjunction with X-ray scattering and modeling approaches to unravel nanoscale structural insights in highly heterogeneous polymer bends. These results are then correlated and complemented by bulk optoelectronic properties, which provide specific recommendations for the creation of next generation of molecular electronics. Our research benefits from close collaborations with Prof. TQ Nguyen and Prof. GC Bazan groups (UCSB).

Self-assembly and supramolecular materials

Self-assembly of small molecules into functional supramolecular assemblies is of great current interest to develop materials for drug delivery, environmental remediation and optoelectronic applications. Molecular-level understanding assembly and disassembly pathways is expected to help to better formulate supramolecular materials for such applications. Our approach is to apply in situ and ex situ NMR spectroscopy techniques to uncover the molecular self-assembly in solution, soft matter and in the solid-state. Recent results demonstrate that the existence of stable supramolecular structure in solution or in the solid-state may not reflect its integrity in another phase such as, for example, in gel phase or an intermediate phase. Such findings are of paramount importance and open new avenues in the areas of supramolecular chemistry and materials science: several opportunities could be envisaged such as understanding noncovalent assemblies, host–guest complexes, adaptive materials, hydrogels, xerogels and organogels, drug delivery systems, organic–inorganic hybrid materials and active pharmaceutical ingredients, for which transition from solution or gel to the solid‐state, or vice versa, would impact the structure and function.

Hybrid perovskites

Mixed dimensional hybrid perovskite halides are of considerable interest for their application in high efficiency solar cells. These materials exhibit unprecedented power conversion efficiency of over 25% in a single junction solar cell and over 29% in a tandem architecture with crystalline silicon (c-Si). Nevertheless, there are stability issues associated these materials with respect to moisture, light and temperature. This is a major bottleneck to the larger scale production and commercialization of perovskite-based solar cells. Reaching a consensus of how these materials behave when exposed to ambient conditions. To this end, accurate understanding of degradation pathways of PSC compositions and their associated structure-property relationships is expected to better formulate hybrid perovskite material compositions, paving the way towards achieving stable efficient solar cells. Our interests lie in the characterization of organic-inorganic interfaces and dynamics of organic cations in low-dimensional perovskite halides, defect passivated and surface passivated perovskite thin films and 2D Ruddlesden-Popper (RP) phases.