2020 Fiscal Year Research-status Report
Imaging ultrafast photocarrier trapping in perovskite photovoltaic materials
| Project/Area Number |
19K05637
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| Research Institution | Okinawa Institute of Science and Technology Graduate University |
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Principal Investigator |
Dani Keshav 沖縄科学技術大学院大学, フェムト秒分光法ユニット, 准教授 (80630946)
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| Project Period (FY) |
2019-04-01 – 2022-03-31
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| Keywords | time-resolved PEEM / perovskite photovoltaics |
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| Outline of Annual Research Achievements |
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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| Current Status of Research Progress |
Current Status of Research Progress
1: Research has progressed more than it was originally planned.
Reason
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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| Strategy for Future Research Activity |
Identifying benign and detrimental defects: The second study identifying multiple types of defects and their role in performance losses has been completed. We are now in the process of writing up the findings and preparing a manuscript for submission. We expect to use the last year of the Kakenhi in preparing the manuscript.
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[Journal Article] Performance-limiting nanoscale trap clusters at grain junctions in halide perovskites2020
Author(s)
T.A.S.Doherty, A.J.Winchester, S.Macpherson, D.N.Johnstone, V.Pareek, E.M.Tennyson, S.Kosar, F.U.Kosasih, M.Anaya, M.Abdi-Jalebi, Z.Andaji-Garmaroudi, E.L.Wong, J.Madeo, Y.-H.Chiang, J.-S.Park, Y.-K.Jung, C.E.Petoukhoff, G.Divitini, M.K.L.Man, C.Ducati, A.Walsh, P.A.Midgley, K.M.Dani, S.D.Stranks
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Journal Title
Nature
Volume: 580
Pages: 360-366
DOI
Peer Reviewed / Open Access / Int'l Joint Research
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