Development of An Unprecedented Time- and Space-Resolved Spectroscopy to Evaluate Two-Dimensional Charge Carrier Mobility

2017 Fiscal Year Final Research Report

• Project/Area Number: 15K13816
• Research Category: Grant-in-Aid for Challenging Exploratory Research
• Allocation Type: Multi-year Fund
• Research Field: Device related chemistry
• Research Institution: Osaka University
• Principal Investigator: Saeki Akinori 大阪大学, 工学研究科, 准教授 (10362625)
• Project Period (FY): 2015-04-01 – 2018-03-31
• Keywords: 有機エレクトロニクス / 時間分解マイクロ波伝導度 / 空間分解 / 有機太陽電池

Outline of Final Research Achievements

To comprehensively examine charge carrier transport and relaxation, a new technique combining time-of-flight (TOF) and time-resolved microwave conductivity (TRMC) using a harmonic cavity is developed. The TOF analysis affords long-range hole mobilities of 10^-4 to 10^-2 cm2V-1s-1 for polymer:methanofullerene bulk heterojunction (BHJ) films (P3HT, PffBT4T, and PCPDTBT blended with PCBM), while TRMC transients are simultaneously recorded under an external electric field. The latter exhibits the acceleration of decay with increasing bias voltage. By analyzing the transient photocurrents and TRMC decays based on a diffusion theory with bulk charge recombination, hole relaxation is observed as a function of time (nanoseconds to microseconds) or distance (~micrometers). Contrasting results are found among the BHJ films, which are consistent with the optimal thickness of the organic solar cells and provide the basis to interpret charge carrier dynamics from the spatiotemporal viewpoint.

Free Research Field

有機エレクトロニクス