| 研究実績の概要 |
BACKGROUND: With power conversion efficiencies exceeding 25%, Hybrid Organic-Inorganic Perovskite (HOIP) materials have emerged as very promising photovoltaic materials. However, the presence of defect states remains a major problem. A study of the nanoscale distribution of these defect states, their electronic properties, and the ultrafast photocarrier trapping process at these sites will help improve this technology.
PROPOSAL: In this study, I proposed to apply time resolved photoemission electron microscopy (TR-PEEM) [Nature Nanotech 12, 36 (2017), Science Advances 4, eaat9722 (2018)] to study the nanoscale spatial distribution of defect states in HOIP films, their electronic structure, and their role in ultrafast photocarrier trapping.
RESEARCH PROGRESS: In FY2019, we obtained high quality images of the nanoscale distribution of defects using PEEM, and video of charge trapping using TR-PEEM. We correlated these with PL and AFM, revealing the important role of diffusion. This work was published in Nature 580, 360 (2020). In FY2020, we identify that there were multiple types of defects with surprising differences in their impact on device efficiency. Small, grain boundary defects turned out to be the most detrimental. Polytype defects were the most abundant. Large PbI2 defects were largely benign. Grain boundary defects could be healed with light and oxygen treatment, while the polytypes were unaffected. Currently, we are preparing a manuscript with these findings.
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| 現在までの達成度 (区分) |
現在までの達成度 (区分)
1: 当初の計画以上に進展している
理由
After we were able to easily make images of the defects with PEEM, we were able to progress quite rapidly in understanding the nature of these defects, and their role in carrier trapping.
While the first results were published in 2020 - (Nature 580, 360 (2020)), we are in the process of preparing the second publication from these results.
Thus, we believe that we progressed more smoothly than originally expected.
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