The objective of this EArly-Concept Grant for Exploratory Research (EAGER) award is to elucidate the fundamental microscopic processes that are responsible for metastability in hydrogenated nanocrystalline Si (nc-Si:H). Hydrogenated nanocrystalline silicon (nc-Si:H) with improved optoelectronic properties is important for cost-effective photovoltaics and high-performance optoelectronic devices. However, the electrical properties of nc-Si:H produced using existing technologies degrade under light exposure (light induced degradation) due to the generation of metastable defects. The origin of the defects and their effect on light absorption and charge transport at the nanoscale has been under debate for a long time. The proposed study will utilize a unique combination of novel scanning probe microscopy-based optoelectronic characterization and first-principles simulation of charge transport through crystalline and amorphous regions to quantify the role of various microscopic processes underlying the metastability.
If successful, this interdisciplinary collaborative effort will help develop highly stable nc-Si:H that can be incorporated into advanced solar cell designs. The proposed effort will encourage the participation of Native Americans into higher education. Native Americans represent about 8.5% of the population in South Dakota, and attracting this community into science and technology areas has been a challenge. SDSU's College of Engineering has developed an active outreach program to motivate Native American high-school students towards higher education (SDSU-Flandreau Indian School Success Academy). This project includes a workshop on solar energy for Native American high-school and middle-school students. A new graduate course in nanoscale imaging of PV materials will be developed, and multiple graduate and undergraduate courses will be enhanced.
Major outcomes: Intellectual Merit: This interdisciplinary collaborative effort helped increase fundamental understanding of defect formation in nanocrystalline silicon and amorphous silicon. The research includes study of defect formation in thin films deposited using physical vapor deposition and plasma enhanced chemical vapor deposition (PECVD). Investments in Research Infrastructure: This EAGER award is the first major research grant for photovoltaics team at South Dakota State University. This grant helped convincing the university to invest in research infrastructure, specifically in advanced materials and processing. A major investment includes development of a 3600 Sq Ft state-of-the-art cleanroom facility designed by the PI. Prioritization of research infrastructure will help the department and college to establish sustained research programs. Broader Engagement: This grant supported active outreach program to encourage the participation of underrepresented groups in higher education. Annual workshops for Native American ((SDSU-Flandreau Indian School Success Academy; St Joe’s Middle School) and female K-12 students were conducted to stimulate their interest in STEM education. The PI has visited tribal and K-12 schools, and interacted with students and teachers. Several hundred students have participated in the workshops, and many have gone on to enroll in SDSU and other universities. Integration of Research and Education: REU supplemental grants, and NSF-sponsored REU Site: Simulation and Analysis at South Dakota State University helped hiring over 10 undergraduates to conduct state-of-the-art research. All the REU students have performed well in their research projects and have presented their results at international conferences. The PI has served as South Dakota State Coordinator for NanoDays, a nationwide program to encourage STEM education and awareness about nanotechnology. A new graduate course Nanoscale Imaging was developed. Two graduate courses (Sensors, Electronic Materials) and one undergraduate course (Electronic Materials & Devices) were enhanced. Manpower Development: Over twenty graduate and undergraduate students and postdocs were supported. The cohorts went onto pursue careers in high-technology areas (Samsung, Intel, NASCEN Technology etc.) and academia (Lehigh, Houston Energy Research Park, McGill University). Outreach: The PI served as lead organizer for two symposia at Materials Research Society’s 2010 Spring and 2011 Fall meetings. Over 6000 researchers from 60 countries have attended each of these meetings. The PI has delivered tutorial lectures on nanoscale charge transport in photovoltaic devices. 2010 Spring: Nanoscale Charge Transport in Excitonic Solar Cells 2011 Fall: Fundamental Processes of Solar Harvesting in Excitonic Solar Cells The PI’s experiences in establishing research infrastructure and building multidisciplinary research teams helped presenting a case-study to the White House Office of Science & Technology (OSTP) policy on Sustaining Research Programs in Smaller Universities (2013).
