Direct observation of UV-induced accumulated charges in inverted-type polymer solar cells with TiO_x layer by electron spin resonance

ABSTRACT

We present an electron spin resonance (ESR) study of inverted-type polymer solar cells with the structure of indium tin oxide (ITO)/amorphous titanium oxide (TiO_x)/regioregular poly(3-hexylthiophene) (P3HT):phenyl-C₆₁-butryic acid methyl ester (PCBM)/Au. Two light-induced ESR signals with narrow and broad linewidth were observed by light irradiation. We found a strong correlation between typical light-soaking effects and the ESR signal with the broad linewidth under UV light irradiation. From the fact that the light-soaking effect requires UV irradiation, the ESR signal with the broad linewidth is found to be related with the light-soaking effect.

KEYWORDS:

• inverted-type polymer solar cell
• electron spin resonance
• titanium oxide
• light-soaking effect

Acknowledgments

This work was supported by a Grant-in-Aid for Scientific Research (24560004) from JSPS.