Correlation between Inner Electric Field and Photocurrent of Zn-Phthalocyanine Schottky-Barrier Cells

概要

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An electroabsorption (EA) study is carried out at an electric-field modulation frequency $\omega_{\text{m}}/(2\pi)$ of 1 Hz for two types of typical organic Schottky-barrier cell, namely, Au/Zn-phthalocyanine (ZnPc)/Al and Au/ZnPc/In/Al, in order to elucidate the role of the inner electric field in photocurrent ($I_{\text{photo}}$) generation. From the bias dependence of the 1F- and 2F-EA intensities measured at the frequencies of $\omega_{\text{m}}$ and $2\omega_{\text{m}}$, respectively, it is shown that the inner electric field $E_{0}$ as well as the modulation electric field $E_{\text{m}}$ is quenched in the ZnPc layer with a forward bias larger than ${\sim}1$ V. For Au/ZnPc/Al, a good correlation is observed between $E_{0}$ and $I_{\text{photo}}$, which indicates that $I_{\text{photo}}$ is generated by $E_{0}$. For Au/ZnPc/In/Al, on the other hand, no correlation is observed between $E_{0}$ and $I_{\text{photo}}$. An interpretation of the latter is that $I_{\text{photo}}$ is caused by an increase in charge-injection probability at the ZnPc/In interface as a result of the trapping of photogenerated charges in the interface region. For both systems, the depletion layer is detected by capacitance-voltage measurement at 0.2 Hz.
Published by the Japan Society of Applied Physics through the Institute of Pure and Applied Physicsの論文
2005-01-15