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2019 Fiscal Year Final Research Report

Creation of spin semiconductor solar energy conversion device

Research Project

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Project/Area Number 17K18870
Research Category

Grant-in-Aid for Challenging Research (Exploratory)

Allocation TypeMulti-year Fund
Research Field Electrical and electronic engineering and related fields
Research InstitutionThe University of Tokyo

Principal Investigator

Tabata Hitoshi  東京大学, 大学院工学系研究科(工学部), 教授 (00263319)

Project Period (FY) 2017-06-30 – 2020-03-31
Keywordsエネルギー変換 / 太陽光 / スピン秩序 / 極性制御 / 光水分解
Outline of Final Research Achievements

In order to achieve an unassisted water splitting for a single photoanode PEC device, Fe1.5Al0.5O3 was studied. It is said that Fermi level pinning will happen when mid-bandgap energy states resulting from both oxygen vacancies and crystalline disorder that can trap holes at the surface exist. This may be one explanation for our result. But a more likely explanation is a limitation for Fermi level shift in Fe2O3-based material. The polaron state level for Fe3+ reduction to Fe2+ will trap photogenerated electrons in 2 ps , which is much faster than free electron transport or transfer. So the upper limit of fermi level or quasi-Fermi level generated by illumination is this polaron state level. To over come this limitation, we need add a non-polaron electronic transport mechanism into our Al-substituted hematite, so that the quasi-Fermi level can shift over polaron state and hydrogen redox potential. Finally, the unassisted PEC water splitting is achieved.

Free Research Field

機能材料科学、酸化物エレクトロニクス、バイオエレクトロニクス・フォトニクス

Academic Significance and Societal Importance of the Research Achievements

α-Fe2O3は赤さびの主成分で安価・安定な物質であるが600nm以上の波長域では光電変換できない問題点があった。本研究成果はdバンド電子論的見地からα-Fe2O3に4d、5d遷移金属を置換して電子軌道混成によるバンドギャップ狭帯化で、可視光波長域の光電変換の高効率化と近赤外光領域の利用を可能とした。更に従来積極的な利用がされてこなかった“スピン配列”に着目し、スピン三重項状態を利用した励起キャリア長寿命化による高効率化を目指した。従来からの酸化鉄光電極の研究では、殆どが表面構造を制御して光吸収の増大を試みていた。今回の成果は太陽光エネルギー利用の新たな可能性を示すものと考える。

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Published: 2021-02-19  

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