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We demonstrate, by means of light-induced EPR and optical spectroscopy, that thermal treatment of P3HT/PCBM films prepared from CB solution results in a decrease of the charge transfer yields. The improved performance of solar cells is therefore attributed to optimization of the morphology, in particular molecular order in the P3HT regions, which could be monitored by optical absorption and resonant Raman scattering (RRS). We further found that spin coating from slowly evaporating solvents leads directly (i.e., without thermal treatment) to optimal morphologies of the P3HT/PCBM films, with similar results for charge transfer, morphology and solar cell efficiencies. [ABSTRACT FROM AUTHOR]

We propose a novel approach to thin‐film silicon solar cells, namely the freestanding monocrystalline silicon layer transfer process with heterojunction emitter (FMS‐HJ). High crystallographic quality mono‐Si films were deposited on freestanding porous silicon (PS) films by chemical vapor deposition (CVD). These free‐standing mono‐Si (FMS) films were processed into solar cells by creating a‐a‐Si/c‐Si heterojunction. In our preliminary experiments a thin‐film FMS‐HJ solar cell with 9.6% efficiency was realized in a 20‐μμm‐thin active layer. Copyright © 2005 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Hydrogenated amorphous silicon (a-Si : H) layers deposited by chemical vapour deposition provide an attractive route to achieve high-performance crystalline silicon (c-Si) solar cells due to their deposition at low temperatures and their superior passivation quality. Hydrogen certainly plays an additional crucial role by passivating the dangling bonds, and thus improving the electrical and optical properties. In this work, we present the variation of the effective lifetime with the hydrogen dilution ratio R  =  (H2/SiH4). We find that at lower hydrogen dilution rates (R  <  2), the polymerization reaction of silane molecules in the plasma bulk as well as the excess of dihydride (Si–H2) incorporation in as-deposited layers result in higher microvoid density and worse passivation quality. In contrast, the deposition at higher hydrogen dilution rates (R  >  5) leads to a degradation in the film quality with very low hydrogen content and crystalline epitaxial growth at the a-Si/c-Si interface. Thus, the best material quality is obtained just below the onset of amorphous-to crystalline transition (R  =  3), which favours further improvement of the passivation during a post-deposition annealing. [ABSTRACT FROM AUTHOR]

Nanoimprint lithography is used to directly pattern the conjugated polymer semiconductor poly(3-hexylthiophene) (P3HT). We obtain trenches with aspect ratios up to 2 and feature sizes as small as 50 nm in this polymer. The application to organic solar cells is shown by creating an interpenetrated donor-acceptor interface, based on P3HT and N,N'-ditridecyl-3,4,9,10-perylenetetracarboxylic diimide (PTCDI-C13), deposited from the vapor phase to reduce shadow effects. A planarizing layer of spin-coated zinc oxide (ZnO) nanoparticles is used to reduce the roughness of the layer stack. The response of the photovoltaic devices follows the increased interface area, up to a 2.5-fold enhancement. [ABSTRACT FROM AUTHOR]