We study the photoinduced degradation of hybrid organometal perovskite photovoltaics under illumination and ambient atmosphere using UV-vis absorption, atomic force microscopy, and device performance. We correlate the structural changes in the surface of the perovskite film with changes in the optical and electronic properties of the devices. The photodecomposition of the methylammonium lead triiodide perovskite layer itself proceeds much more slowly than the photodegradation of the performance of devices with fullerene/bathocuproine/aluminum top contacts, indicating that the active layer is more stable than the interface with the electrodes in this geometry. The evolution of the perovskite active layer performance proceeded through several phases: (1) an initial improvement in device characteristics, (2) a plateau with very slow degradation and finally (3) a catastrophic decline in material performance accompanied by marked changes in film morphology. The rapid increase in surface roughness of the active perovskite semiconductor associated with sudden failure also correlates with decreased absorption at the perovskite band edge and growth of a lead iodide absorption feature. We find that degradation requires both light and moisture, is accelerated at increased humidity, and scales linearly with light intensity, depending primarily on total photon dose.

A series of arylated dihydrofullerene derivatives were synthesized to elucidate the effective design of fullerene derivatives for enhancing the performance of organic photovoltaics. The LUMO energy of the fullerenes was estimated by the first reduction potential and theoretical calculations. The results showed that the methoxy groups substituted at spatial proximity to the fullerene core offered significant stabilization of the LUMO level. The stabilizing effect of the directly arylated fullerenes is more significant than that of conventional methanofullerenes. The theoretical investigation was performed with regard to the electronic interaction between the methoxy and fullerene moieties.

Novel fluorinated subnaphthalocyanine derivatives were newly designed and synthesized as donor materials for low molecular organic photovoltaic cells using fullerene as an acceptor. They were designed to have the low-lying HOMO energy levels for improvement of open circuit voltage without any expense of short-circuit current density. The HOMO/LUMO energy levels of hexafluoro-, heptafluoro-, dodecafluoro-, tridecafluoro-and the parent subnaphthalocyanine estimated based on the photoelectron spectroscopy were-5.69/-3.93,-5.67/-3.90,-5.96/-4.19,-5.92/-4.11 and-5.30/-3.58 eV, respectively, showing that frontier orbital energy levels can be effectively tuned by fluorination.

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Novel organoboron polymers containing pyrazaboles in the main chain were prepared by Heck-Sonogashira coupling. The coupling reaction between diyne monomers and pyrazabole derivatives gave the corresponding polymers in good yields. The number-average molecular weights of the obtained polymers were relatively high compared with the organoboron polymers prepared by hydroboration polymerization. The obtained polymers were further investigated by UV-vis absorption and fluorescence spectroscopy.