Development of carrier observation method based on ESR techniques in organic semiconductor photodevices

2014 Fiscal Year Final Research Report

• Project/Area Number: 24654087
• Research Category: Grant-in-Aid for Challenging Exploratory Research
• Allocation Type: Multi-year Fund
• Research Field: Condensed matter physics I
• Research Institution: Nagoya University
• Principal Investigator: SHIN-ICHI Kuroda 名古屋大学, 工学(系)研究科(研究院), 教授 (20291403)
• Project Period (FY): 2012-04-01 – 2015-03-31
• Keywords: 共役高分子 / フラーレン / 電子スピン共鳴 / 光伝導 / 有機電界効果トランジスタ / 有機光電変換デバイス

Outline of Final Research Achievements

The blend films of conducting polymers and fullerenes have been widely studied for photovoltaic applications. In this study, conduction and recombination mechanisms of charge carriers in these blend films are clarified by using electron spin resonance (ESR) spectroscopy, together with the conductivity measurements. The blends using semicrystalline polymers exhibit quadrimolecular recombination kinetics of photogenerated carriers, where two positive polarons on the polymer chain and two fullerene radical anions annihilate simultaneously, up to room temperature. This process presumably originates from the formation of doubly-charged bipolarons on the ordered polymer chain. In addition, carrier mobilities are directly determined from the FET characteristics. The hole mobility depends on the mixing ratio of the fullerene through the change of polymer orientation. It is clarified that the photon-to-current efficiency shows maximum where the electron and hole mobilities match each other.

Free Research Field

有機固体物性、磁気共鳴