Synthesis of Widely Fermi Level Tunable Organic Semiconducting Materials Based on Supraatomic Doping Concept

2020 Fiscal Year Final Research Report

• Project/Area Number: 19K15387
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 28030:Nanomaterials-related
• Research Institution: Tohoku University
• Principal Investigator: Ueno Hiroshi 東北大学, 学際科学フロンティア研究所, 助教 (00775752)
• Project Period (FY): 2019-04-01 – 2021-03-31
• Keywords: 有機半導体 / ドーピング / フラーレン / 超原子 / ナノ粒子 / ペロブスカイト太陽電池

Outline of Final Research Achievements

A new neutral Li@C60 endohedral fullerene derivative, Li@PCBM, was synthesized and characterized. The material has a strikingly similar molecular structure to empty PCBM but different number of electrons. Such a unique feature enables the Li@PCBM and empty PCBM pair to induce effective doping without distortion of crystallinity. According to the novel doping concept, Li@PCBM:PCBM hybrid semiconducting thin film was prepared. The addition of Li@PCBM to empty PCBM raised the Fermi level of PCBM thin film by 0.12 eV, which clearly indicated the electron-donating behavior of Li@PCBM to empty PCBM. By utilizing the n-doped PCBM thin film, perovskite solar cells were fabricated. Photovoltaic parameters, VOC, JSC, and FF were clearly improved, and ca. 3% higher power conversion efficiency than control device was obtained at optimal doping concentration.

Free Research Field

ナノ材料科学，物理有機化学

Academic Significance and Societal Importance of the Research Achievements

有機半導体分子と外観構造が全く同じであるにも関わらず，電子の数が1つだけ違うという特異な関係にある分子の合成に成功し，このような特異な関係にある２分子を用いた新ドーピング概念：超原子ドーピングを提唱により，既存有機半導体の物性チューニングが可能であることを示した．本研究により，再生エネルギーの鍵となる太陽電池等の有機デバイスに利用される有機半導体材料の高性能化，汎用化を支える重要な基礎的知見が得られた．