Current Projects

Synthesis of cross-conjugated benzobisoxazoles

Benzo[1,2-d:4,5-d′]bisoxazoles (BBO)s are promising electron-deficient heterocycles for use the development of new polymers due to their near-planar structure which can facilitate efficient packing and charge transport. Materials based on them have exceptional electronic, optical and thermal properties and thus are ideally suited for diverse organic semiconducting applications. BBO-based systems are unique in that they have two conjugation pathways, one along the 2,6-axis that encompasses the two oxazole rings and a second along the 4,8-axis that goes through the central benzene ring. This structure allows for synthesis of number of cross-conjugated materials with properties that are readily tuned by substitution. Using a combination of organic synthesis, theoretical calculations and physical measurements we are systematically investigating the structure property relationships within these systems. The work has produced wide band-gap blue-light emitting materials for use in OLEDs and narrow band gap cruciform with energy levels suitable for use in OSCs. This project is supported by the NSF Division of Chemistry, CHE-1640298 (1413173).

Synthesis of novel materials based on benzodichalogenophenes (BDC)s

Based on successful the ring annulation chemistry developed by Richard Larock, our group has been developed an efficient route for the synthesis of substituted benzo[1,2-b:4,5-b’]difuran (BDF). This electron-rich building block is easily synthesized in a few high yielding steps from low-cost starting materials; readily customizable enabling a number of structural modifications; and isoelectronic to benzo[1,2-b:4,5-b’]dithiophene. The later, has been combined with various electron-deficient co-monomers for the synthesis of copolymers with excellent performance in organic solar cells (OSC)s. Due to the differences in the electronic structure of BDF, its performance in OPVs is expected to exceed that of the sulfur analog. We are currently evaluating the impact of atomic engineering on the materials properties by performing structural modifications on the basic polymer structure are also proposed to improve film formation, pi-stacking and charge transport. Concurrently, we evaluate the physical, optical, and electronic properties of the materials through spectroscopic measurements and performance in OSCs. This project is supported by the NSF Division of Materials Research, DMR-1640297 (1410088).

Application of the OSCs in OLED and OPV Devices

The BBO materials that we design and synthesize are tested as dopants/guests in “host-guest” OLED devices built our MODEL facility. We optimize the device architecture by utilizing a variety of charge transport and host materials. We also build the OLED stacks via solution processing (such as spin coating) and/or vapor deposition of the layers. We then evaluate their device performance metrics – brightness, external quantum efficiency (EQE), current density, current efficiency and power efficiency.

The BDF materials that we develop are utilized in bulk heterojunction OPV devices, also built in our MODEL facility. The BDF small molecules show promise as non fullerene accetpors and hole transport materials and the polymers are tested as donors in BHJs. The devices are tested in the MODEL facility and their key performance metrics are measures – Voc, Jsc, Fill factor, etc.

Machine Learning for the prediction of OLED properties

We utilize a simple ML model developed in collaboration with Prof. Eric Kolaczyk (McGill University) to predict emission wavelengths of our BBO molecules, to help in rapid screening and selection of target molecules. We compute the opto-electronics properties via DFT and use this is combination with experimental data of new molecules to grow the dataset of our models. We aim to incorporate HTE to further accelerate screening of the materials and improving the quality and quantity of our dataset.

Synthesis of conjugated oligomers in flow

Flow microreactors have emerged as a promising new synthetic method for both lab scale and industrial chemists. Microreactors have several advantages over traditional batch methods such as enhanced heat transfer, safety when performing exothermic or toxic reactions, precise control of resonance or reaction time, high throughput, and high surface to volume ratio. As a result, the use of flow reactors has been used to optimize a variety of pharmaceutical processes. Therefore, it is our intention to utilize a platform that is familiar in biology and medicinal chemistry to investigate a variety of carbon-carbon bond forming techniques, and apply them using flow chemistry to generate well-defined, oligomeric materials of varying molecular weight. The overall objective is to identify trends in conjugation length to gain a deeper understanding of effective conjugation and how it effects both optoelectronic and film forming properties in a variety of materials.