Spectroscopic second harmonic generation measured on plasma-deposited hydrogenated amorphous silicon thin films

Optical second harmonic generation (SHG) has been measured for plasma-deposited thin films of hydrogenated amorphous silicon (a-Si:H) at different polarization states for pump photon energies between 1.0 and 1.7 eV. Distinct resonance peaks are observed in this energy range and it is shown that the SH signal originates from an isotropic contribution at both the film-surface and substrate-interface region. The possibility that the SH signal originates from surface and interface dangling bond states of a-Si:H is discussed

In-situ compositional and structural analysis of plastic solar cells

Bulk-heterojunction photovoltaic cells consisting of a photoactive layer of poly[2-methoxy-5-(3',7'-dimethyloctyloxy)-1,4-phenylenevinylene] and a C60 deriv., 1-(3-methoxycarbonyl)propyl-1-phenyl-[6,6]-methanofullerene, (PCBM), sandwiched between an indium tin oxide anode covered with poly(ethylene dioxythiophene):poly(styrene sulfonate) (PEDOT:PSS), and an Al cathode, were analyzed using TEM and cryogenic Rutherford backscattering spectrometry (RBS) to assess the structural and elemental compn. of these devices. Sample cross sections of fully processed photovoltaic cells were prepd. with the focused ion beam technique. TEM of these samples revealed the individual layers and their interfaces. RBS shows that during prepn., diffusion of In into the PEDOT:PSS occurs while the diffusion of Al into the polymer layers is negligible. An iodinated C60 deriv. (I-PCBM) was used to det. the concn. profile of this deriv. in the vertical direction of a 100 nm thick active laye