By using time-resolved electric-field-induced optical second-harmonic generation (EFISHG) measurement, we directly probed photovoltaic effect generated in double-layer (pentacene/C60) organic solar cells (OSCs). The electric field in C60 layer was selectively probed by using incident laser with a wavelength of 1,000 nm. Results showed that excess positive charges Qs=1.5×10-8 C/cm2 accumulated at the pentacene/C60 interface under photoillumination. These charges generated the interfacial voltage Vs=0.16 V and deformed a potential profile in the OSCs. The EFISHG measurement is an effective way for directly catching carrier behavior at the double-layer interface in OSCs in terms of the photovoltaic effect.

By using optical electric-field-induced second-harmonic generation (SHG) measurement, we directly probed charge accumulation and decay processes in double-layer [copper-phthalocyanine (CuPc)/C60] organic solar cells (OSCs). Results showed that negative excess charges accumulated at the CuPc/C60 interface under photoillumination and the charges decayed in a two-step process in dark. Analysis using the filtering method showed that 24% of the accumulated negative excess charges decayed with a lifetime τL1=5.3×10−5 s and the other 76% of charges decayed with a lifetime τL2=6.2×10−2 s. We conclude that analyzing SHG signal response provides a direct way to investigate carrier lifetime in multilayer OSCs.

By using time-resolved optical electric-field-induced second-harmonic generation measurement, we directly probed photo-voltage generation process in organic double-layer (pentacene/C60) solar cells. Results showed that photoillumination induced negative excess charge Qs = −3.6 × 10−9 C/cm2 at the pentacene/C60 interface, and the induced charge caused generation of the open-circuit voltage 0.26 V. Using an equivalent circuit based on a Maxwell-Wagner (MW) effect model well accounted for the excess charge accumulation process. The MW model analysis also well accounted for the open-circuit voltage, the short-circuit current, and the fill-factor of organic solar cells (OSCs). We concluded that the excess charges due to the MW effect give a significant effect on the photovoltaic effect of OSCs.

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By irradiating evaporated 10,12-pentacosadiynoic acid (p-DA) monomer film with circularly polarized light (CPL), we prepared chiral poly (diacetylene) [PDA] film. The induced chirality was dependent on the rotational direction of the CPL. It was shown that the induced chirality increased with the PDA domain size, regulated by the substrate temperature. AFM image exhibited a morphological evidence of the chirality induced in the PDA film at high substrate temperature.

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