Michael Meister

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Despite significant study, the precise mechanisms that dictate the efficiency of organic photovoltaic cells, such as charge separation and recombination, are still debated. Here, we directly observe efficient ultrafast free charge generation in the absence of field in annealed poly(3-hexylthiophene):methanofullerene (P3HT:PCBM). However, we find this(More)
We report the fabrication and characterization of wavelength-scale diffractive optical elements etched directly on the surface of red (660 nm) vertical-cavity surface-emitting lasers. The structures were fabricated by focused ion beam etching. Linear and two-dimensional (2-D) grating configurations were investigated. Each showed excellent suppression of the(More)
The precise mechanism and dynamics of charge generation and recombination in bulk heterojunction polymer:fullerene blend films typically used in organic photovoltaic devices have been intensively studied by many research groups, but nonetheless remain debated. In particular the role of interfacial charge-transfer (CT) states in the generation of free charge(More)
In hybrid solar cells a blocking layer between the transparent electrode and the mesoporous titanium dioxide is used to prevent short-circuits between the hole-conductor and the front electrode. The conventional approach is to use a compact film of titanium dioxide. This layer has to be of optimum thickness: it has to cover the rough surface of the anode(More)
New trans-AB2C meso-substituted porphyrin amino acid esters with meso-substituents of tunable electron withdrawing power (B = mesityl, 4-C6H4F, 4-C6H4CF3, C6F5) were prepared as free amines 3a-3d, as N-acetylated derivatives Ac-3a-Ac-3d and corresponding zinc(II) complexes Zn-Ac-3a-Zn-Ac-3d. Several amide-linked bis(porphyrins) with a tunable electron(More)
The synergy of push-pull substitution and enlarged ligand bite angles has been used in functionalized heteroleptic bis(tridentate) polypyridine complexes of ruthenium(II) to shift the (1) MLCT absorption and the (3) MLCT emission to lower energy, enhance the emission quantum yield, and to prolong the (3) MLCT excited-state lifetime. In these complexes, that(More)
A hybrid blocking layer consisting of a conducting TiO2 network embedded in a ceramic matrix is implemented in a solid-state dye-sensitized solar cell. This novel type of blocking layer is thinner than the classical blocking layer films as shown with SEM and XRR measurements, and thereby the conductivity of the hybrid film is increased by 110%. A(More)
Recently, the performance of ZnO nanocrystals as an electron acceptor in a solar cell device was significantly increased by a semiconducting surfactant. Here we show, using transient absorption spectroscopy and a parallel pool analysis, that changes in the quantum efficiency of charge generation account for the performance variation among(More)
The dependence of the thin film morphology and excited-state dynamics for the low-bandgap donor-acceptor copolymer poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b']-dithiophene)-alt-4,7-(2,1,3-benzothiadiazole)] (PCPDTBT) in pristine films and in blends (1:2) with [6,6]-phenyl-C(61)-butyric acid methyl ester (PCBM) on the use of the solvent(More)
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