We demonstrate up-conversion of noncoherent sunlight realized by ultralow excitation intensity. The bimolecular up-conversion process in our systems relies on the presence of a metastable triplet excited state, and thus has dramatically different photophysical characteristics relative to the other known methods for photon up-conversion (two-photon absorption, parametric processes, second harmonic generation, sequential multiphoton absorption, etc.).

An emitter/sensitizer couple (see picture; C red/green, H white, N blue, Pd gray) was specially designed for the process of noncoherently excited photon up‐conversion. The hypsochromic shift between the energy of the excitation photons and the emitted photons is about 0.7 eV, and an external quantum yield of 0.04 is achieved. As noncoherent excitation source, the near‐infrared part of the solar spectrum was used.

Dye-sensitized solar cells have established themselves as a potential low-cost alternative to conventional solar cells owing to their remarkably high power-conversion efficiency combined with 'low-tech' fabrication processes. As a further advantage, the active layers consisting of nanoporous TiO2 are only some tens of micrometres thick and are therefore in principle suited for flexible applications. However, typical flexible plastic substrates cannot withstand the process temperatures of up to 500 degrees C commonly used for sintering the TiO2 nanoparticles together. Even though some promising routes for low-temperature sintering have been proposed, those layers cannot compete as regards electrical properties with layers obtained with the standard high-temperature process. Here we show that by a lift-off technique, presintered porous layers can be transferred to an arbitrary second substrate, and the original electrical properties of the transferred porous layers are maintained. The transfer process is greatly assisted by the application of composite layers comprising nanoparticles and nanorods.

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The alignment of the electrode Fermi level with the valence or conduction bands of organic semiconductors is a key parameter controlling the efficiency of organic light-emitting diodes, solar cells, and printed circuits. Here, we introduce a class of organic molecules that form highly robust dipole layers, capable of shifting the work function of noble metals (Au and Ag) down to 3.1 eV, that is, ∼1 eV lower than previously reported self-assembled monolayers. The physics behind the considerable interface dipole is elucidated by means of photoemission spectroscopy and density functional theory calculations, and a polymer diode exclusively based on the surface modification of a single electrode in a symmetric, two-terminal Au/poly(3-hexylthiophene)/Au junction is presented. The diode exhibits the remarkable rectification ratio of ∼2·10(3), showing high reproducibility, durability (>3 years), and excellent electrical stability. With this evidence, noble metal electrodes with work function values comparable to that of standard cathode materials used in optoelectronic applications are demonstrated.