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Polymer/fullerene bulk heterojunction solar cells consisting of PDDTP:PCBM blends have been investigated and optimized. The structural properties of the photoactive layers were studied by GID-XRD, which revealed a pronounced response of photovoltaic parameters on the polymer crystallinity. In addition to P3HT, another donor polymer was found that develops crystalline domains upon annealing. We found a clear correlation between annealing time, power conversion efficiency, and polymer crystallinity. The PDDTP crystallization ability is a promising property. This is a first step toward the synthesis of low-bandgap polymers, which likewise show the ability to form crystalline domains and may therefore lead to a substantial increase in efficiency.

In order to develop nanocarbon photoprobes for the DNA molecule estimation in fluids, we have constructed ones using hydrated C60 and C60 derivative aggregates predicting their integration by ds-, ss-DNA molecules in aqueous suspensions. Their photoresponse under UV–vis excitation depends from electronic features of biomolecular surrounding – natural ds-, ss-DNA molecules – was studied by UV–vis absorption and photoluminescence spectroscopy. We detected features in absorption spectra at 275–380 and 235–290 nm ranges and in photoluminescence spectra at 490–635 and 525–635 nm ranges, caused by the absorption and photoluminescence at interface between the C60, C60 derivative cores and the ds-, ss-DNA molecules, respectively. Spectrum analysis is based on models of electrostatic and/or hydrophobic interactions of C60, C60 derivatives with charged phosphate groups and bases of the ds-, ss-DNA molecules in aqueous suspensions.

The evolution of nanomorphology within thin solid-state films of poly(3-alkylthiophene):[6,6]-phenyl-C61 butyric acid methyl ester (P3AT:PCBM) blends during the film formation and subsequent thermal annealing is reported. In detail, the influence of the P3AT's alkyl side chain length on the polymer/fullerene phase separation is discussed. Butyl, hexyl, octyl, decyl, and dodecyl side groups are investigated. All of the P3ATs used were regioregular. To elucidate the nanomorphology, atomic force microscopy (AFM), X-ray diffraction, and optical spectroscopy are applied. Furthermore, photovoltaic devices of each of the different P3ATs have been constructed, characterized, and correlated with the nanostructure of the blends. It is proposed that the thermal-annealing step, commonly applied to these P3AT:PCBM blend films, controls two main issues at the same time: a) the crystallization of P3AT and b) the phase separation and diffusion of PCBM. The results show that PCBM diffusion is the main limiting process for reaching high device performances.

Composite films of P3HT/PCBM-(poly[3-2,5-diyl]/[6,6]-phenyl C61 butyric acid methyl ester) are widely used as an active layer in plastic solar cells. We have studied the influence of thermal annealing on nano-structural and optical properties of thin spin-coated P3HT/PCBM-films. Their structural properties were studied by X-ray diffraction in grazing incidence geometry. It was found that the crystallinity of the investigated films is drastically increased upon annealing. Furthermore, the anisotropic dielectric function of such films was determined by spectroscopic ellipsometry. Significant changes were observed both in parallel and perpendicular components of the dielectric function after annealing. These changes were attributed to the formation of crystalline domains upon annealing.

The photovoltaic action of plastic solar cells based on P3HT/PCBM- (poly[3-hexylthiophene-2,5-diyl]/[6,6]-phenyl C 61 butyric acid methyl ester)-composites depends strongly on structure of the active layer. In this work, the impact of P3HT-crystallinity on optical absorption of P3HT/PCBM-films was investigated. We observed, that both P3HT-crystallinity and optical absorption of thermally annealed films are increased in comparison to the not annealed ones. The highest crystallinity was achieved for films annealed at 125 °C. Further increase of annealing temperature leads to decrease of P3HT crystallinity. It is shown that the absorption coefficient of the films at low photon energies is proportional to the area under the X-ray-diffraction peak, which is a measure for the degree of film crystallinity.

We investigate thin poly(3-hexylthiophene-2,5-diyl)/[6,6]-phenyl C61 butyric acid methyl ester (P3HT/PCBM) films, which are widely used as active layers in plastic solar cells. Their structural properties are studied by grazing-incidence X-ray diffraction (XRD). The size and the orientation of crystalline P3HT nanodomains within the films are determined. PCBM crystallites are not detected in thin films by XRD. Upon annealing, the P3HT crystallinity increases, leading to an increase in the optical absorption and spectral photocurrent in the low-photon-energy region. As a consequence, the efficiency of P3HT/PCBM solar cells is significantly increased. A direct relation between efficiency and P3HT crystallinity is demonstrated.

We have investigated the structural and optical properties of P3OT and P3OT/fullerene thin films in view of their application as active layer in plastic solar cells. Films of these materials were prepared by spin coating from toluene solutions onto silicon substrates. Their optical properties were studied by spectroscopic ellipsometry, which provides the anisotropic dielectric function of the films. Moreover, structural properties were studied using X-ray diffraction. A close correlation between the results obtained by both methods could be found. Especially, the strong optical anisotropy of the films can be explained in terms of a preferable orientation of the polymer chains parallel to the substrate. The effect of the optical anisotropy on the performance of optoelectronic devices is discussed.

Composite films of P3HT/PCBM (poly[3-hexylthiophene-2,5-diyl]/[6,6]-phenyl C61 butyric acid methyl ester) are widely used as active layer in plastic solar cells. It was shown that the annealing of the active layer leads to increased optical absorption and therefore to improved performance of solar cells. However the origin of the improved optical absorption is not clear yet. In this work, structural and optical properties of such films were studied by X-ray diffraction and spectroscopic ellipsometry, respectively. The influence of the annealing temperature on film crystallinity and on optical absorption was studied. A direct correlation between optical absorption and film crystallinity was demonstrated, i.e. increased crystallinity leads to an increased optical absorption. The highest crystallinity and the highest optical absorption were observed for films annealed at 125 °C.

We report on nanomorphology evolution within different poly[3-alkylthiophene]/phenyl C61-butyric acid methyl ester (P3AT/PCBM) blends upon film formation and subsequent thermal annealing. A correlation between achievable solar cell performance and corresponding nanomorphology is drawn in conclusion.