Spin-dependent recombination of photoinduced carriers in phthalocyanine/C60 heterojunctions

Ichiro Hiromitsu, Yoshiaki Kaimori, Mayuko Kitano, and Takashi Ito
Phys. Rev. B 59, 2151 – Published 15 January 1999
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Abstract

Spin-dependent recombination of photoinduced carriers in H2-phthalocyanine (H2Pc)/C60 heterojunctions is studied by electrically detected electron-spin resonance (EDESR) spectroscopy. The EDESR spectrum of the H2Pc/C60 consists of two components A and B, the g values of which are 2.0018±0.0002 and 2.0010±0.0002, respectively. The two components are attributed to exchange-coupled localized electron-hole pairs trapped at different types of recombination centers. Component A has spin-flip satellites due to an interaction between the electron (or hole) spin, and its surrounding nuclear spins of protons which belong to the H2Pc rings. From the satellite intensity, the distance between the electron (or hole) and the protons is estimated to be 4.33±0.25 Å, indicating that the localized pairs for the component A locate close to the H2Pc rings. The spin dynamics of the localized pairs for the component A is studied by a microwave recovery experiment, in which the time dependence of the EDESR signal intensity is measured after turning the resonant microwave on and off. A theoretical model of the spin-dependent recombination of the exchange-coupled electron-hole pair is proposed with which the experimental results of the microwave recovery are explained. By a theoretical analysis, it is found that R1×106 s1 and D+Wsl=6.2(±0.8)×104 s1 for component A at room temperature, where R is the recombination rate of the localized pair in the Sz=0 triplet sublevel, and D and Wsl are the dissociation and the spin-lattice relaxation rates, respectively, of the pairs in the triplet sublevels. The photocurrent I2 that is caused by the dissociation of the localized pairs for component A is about 5% of the total photocurrent.

  • Received 28 May 1998

DOI:https://doi.org/10.1103/PhysRevB.59.2151

©1999 American Physical Society

Authors & Affiliations

Ichiro Hiromitsu, Yoshiaki Kaimori, Mayuko Kitano, and Takashi Ito

  • Department of Material Science, Interdisciplinary Faculty of Science and Engineering, Shimane University, Matsue 690-8504, Japan

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Vol. 59, Iss. 3 — 15 January 1999

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