Computational and Experimental Studies Towards Ideal Organic Semiconductors for Perovskite Solar Cells

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Non-technical Description Perovskite solar cells are an exciting and promising solar cell technology with great potential for the future of renewable energy. However, there are significant technical hurdles to be overcome such as device stability and the cost of materials. This project combines computational and experimental approaches to understand the fundamental design principles of organic semiconductors with desirable properties. These include low-cost, high stability, and efficient charge transport. Such materials could enable the fabrication of inexpensive, efficient, and long-term stable perovskite solar cells. Such organic semiconductors could also have a significant impact on the field of organic optoelectronics. The project will attract female and minority undergraduates and high school students from multiple science and engineering disciplines to participate in research as part of an interdisciplinary team. The project will also foster outreach efforts to K-12 students and the general public. Multiple lectures and demonstrations on two global challenges, renewable energy & circular plastic economy, at K-12 schools and public events per year are planned with the aim of attracting talented students into the renewable energy research field. Technical Description High charge mobility is the critical property that has been targeted by the research community on solution-processable organic semiconductors. In this project, a team of researchers aims at designing and developing such materials possessing not only high charge mobility but also other attributes essential for practical applications such as low cost, high chemical and thermal stability, good film-forming properties, hydrophobicity, and frontier orbital matching specifically for perovskite solar cell applications. Diacenaphtho-fused heterocycle (DAH) cores have been rationally selected and peripheral flexible groups with or without additional functions such as polarity or extended conjugation are computationally evaluated regarding their effects on crystalline order and packing motifs, band energies, and charge mobilities. The systematic and extensive computational studies not only provide promising leads for experimental explorations but also help establish structure-packing motif-charge mobility relationships and crystalize design rules for solution-processable organic semiconductors. Promising targets predicted by theoretical studies are synthesized and their thin film morphological, optical, and charge transport properties are experimentally measured and compared with theoretical predictions. Some DAH derivatives are anticipated to be ideal organic hole-transporting materials that encompass all the desired properties for efficient and stable perovskite solar cells. Those DAHs are used to fabricate perovskite solar cells to gauge their promising potential in simultaneously improving device efficiency, stability, and cost-effectiveness.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.