Demonstration of shift current photovoltaic response in high-quality thin films of halide ferroelectrics

2022 Fiscal Year Final Research Report

• Project/Area Number: 20H02626
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Review Section: Basic Section 29020:Thin film/surface and interfacial physical properties-related
• Research Institution: Institute of Physical and Chemical Research
• Principal Investigator: Nakamura Masao 国立研究開発法人理化学研究所, 創発物性科学研究センター, 上級研究員 (50525780)
• Project Period (FY): 2020-04-01 – 2023-03-31
• Keywords: シフト電流 / 光電変換 / ハライド / 強誘電体 / 分子線エピタキシー

Outline of Final Research Achievements

Materials with broken inversion symmetry exhibit photocurrent driven by quantum-mechanical phase, called shift current. However, experimental demonstration of shift current in thin-film device structures has been lacking. In this study, we target halide ferroelectric semiconductors, which have large spontaneous polarization and strong optical absorption in the visible light range, and demonstrate photovoltaic conversion by shift current mechanism in thin film samples. We first prepared high-quality thin films of ferroelectric halide semiconductors with well-defined polarization axes by molecular beam epitaxy. Then, we successfully observed shift current response in the thin-film device structure. The observed current was found to be enhanced by several orders of magnitude compared to that in bulk samples.

Free Research Field

薄膜界面物性

Academic Significance and Societal Importance of the Research Achievements

本研究では、エピタキシャル薄膜におけるシフト電流応答の実証を行った。トポロジカルな起源を持つシフト電流は、格子欠陥によるキャリアの散乱の影響を受けにくく、パルス光に対して非常に高速の応答性を示すことに加えて、バンドギャップを超える高い電圧出力が可能という特性を持つことから、革新的な光電変換素子の動作原理として期待されている。本研究の成果によって、シフト電流による光電変換の薄膜デバイス動作の研究が今後発展していくことが期待される。