This award is aimed at developing conceptually new two-dimensional semiconducting macromolecules to investigate photovoltaic effect. The proposed two-dimensional macromolecules include discotic liquid crystal (LC) and narrow bad gap oligomer arms. The strong tendency in discotic LC materials to form self assemblies will be used to enhance pi-pi interaction, which will lead to higher charge carriers' mobility. The resulting assembly will possess void spaces that allow the insertion of fulleride derivatives (PCBM) to form interpenetrating networks without interrupting the pi-pi stacking. It is an ideal morphology that will facilitate charge separation and charge transport and benefit the enhancement of the performances of resulting solar cells. New conjugated oligomers with low bandgap and suitable functional groups will be synthesized for further coupling with planar core compounds. Detailed synthesis and characterization of these new macromolecules are proposed. Extensive structural, spectroscopic and morphological characterizations will be carried out on these macromolecules and their corresponding assemblies. Systematic studies on solar cell performances will be carried out in different compositions and processing conditions. The results will provide insightful information on structure/property relationship and new materials for highly efficient solar cells.
NON-TECHNICAL SUMMARY:
This award is aimed at developing conceptually new two-dimensional semiconducting macromolecules for solar cell applications. Fundamental research on synthesis and characterization of these new macromolecules is proposed. The results will provide insightful information on structure/property relationship and new materials for highly efficient solar cells. The proposed materials will push the power conversion efficiency of organic solar cells to 10% and make these devices viable for commercial products. This research activity can have an impact on the national and global effort in developing new and sustainable energy strategy and technologies, thus having an impact on our nation's economy and improving environmental quality by reducing the use of fossil fuels. This research project offers the students involved the opportunity to experience interdisciplinary training and learn the skills to face future scientific challenges. The proposed materials will attract interest from industrial partners and international collaborators. This project provides platforms to allow students to establish collaborations with industrial and international research groups and appreciate the importance of renewable energy research.
This NSF grant supported research effort in developing novel low band gap polymers for high efficient polymer solar cells. During this grant period, more than 20 journal articles have been published. Three graduate students (two women, one minority) have received their doctoral degrees. Three undergraduate students have received training from this program (two of them are women). In the past three years, our research group has made several important discoveries both in the synthesis of new solar cell polymers and the elucidation of photovoltaic effect in BHJ solar cells. The most significant achievements are summarized here. Developed one of the best solar cell polymer systems that lead to single layer power conversion efficiency (PCE) of 9.4% in small solar cells. This value indicates the potential of these materials for further commercial explorations. The new polymers developed have attracted extensive attention from the solar cell community for further device exploration. The new polymer PTB7 is now used world widely for further studies. Discovered a guideline to rationally design new materials based on dipolar changes in polymer repeating unit. The chemistry developed led us to the guideline for further development of low bandgap polymers and allowed synthetic chemists to rationally design polymers before they invoke lengthy synthetic effort. Discovered an effective approach to enhance solar cell efficiency by using dual noble metal (Au and Ag) nanoparticles, Three students graduated with Ph.D. degree and three undergraduate student honor theses are underway. This NSF support promoted PI to be involved in numerous outreach activities, such as scientific writing, seminars and interviews by several non-scientific media. For example, PI gave lectures on solar energy and OPV solar cells in Global School for Advanced Studies (GSAS), organized by Northwestern University and National Taiwan University. This lecture was open to public and a very interesting experience. In collaborations with the TechTransfer office in PI’s institution, the research outcomes were disclosed for intellectual property protection and informed industrial partners. One of the patents is not licensed by an industrial partner (Zhejiang Pharma). These interactions and outreach lead to industrial sponsorship of the PI’s current project and gave students and postdoc. associates opportunity for employment. For example, one student (Briget Carsten) and a postdoc. (Mayank Mayukh) found positions in Intel from which we also received financial support.
